| <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> | |
| <html><head><meta charset="UTF-8"><title>Git User Manual</title><link rel="stylesheet" type="text/css" href="docbook-xsl.css"><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div lang="en" class="book"><div class="titlepage"><div><div><h1 class="title"><a name="id-1"></a>Git User Manual</h1></div></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="preface"><a href="#_introduction">Introduction</a></span></dt><dt><span class="chapter"><a href="#repositories-and-branches">1. Repositories and Branches</a></span></dt><dd><dl><dt><span class="section"><a href="#how-to-get-a-git-repository">How to get a Git repository</a></span></dt><dt><span class="section"><a href="#how-to-check-out">How to check out a different version of a project</a></span></dt><dt><span class="section"><a href="#understanding-commits">Understanding History: Commits</a></span></dt><dd><dl><dt><span class="section"><a href="#understanding-reachability">Understanding history: commits, parents, and reachability</a></span></dt><dt><span class="section"><a href="#history-diagrams">Understanding history: History diagrams</a></span></dt><dt><span class="section"><a href="#what-is-a-branch">Understanding history: What is a branch?</a></span></dt></dl></dd><dt><span class="section"><a href="#manipulating-branches">Manipulating branches</a></span></dt><dt><span class="section"><a href="#detached-head">Examining an old version without creating a new branch</a></span></dt><dt><span class="section"><a href="#examining-remote-branches">Examining branches from a remote repository</a></span></dt><dt><span class="section"><a href="#how-git-stores-references">Naming branches, tags, and other references</a></span></dt><dt><span class="section"><a href="#Updating-a-repository-With-git-fetch">Updating a repository with git fetch</a></span></dt><dt><span class="section"><a href="#fetching-branches">Fetching branches from other repositories</a></span></dt></dl></dd><dt><span class="chapter"><a href="#exploring-git-history">2. Exploring Git history</a></span></dt><dd><dl><dt><span class="section"><a href="#using-bisect">How to use bisect to find a regression</a></span></dt><dt><span class="section"><a href="#naming-commits">Naming commits</a></span></dt><dt><span class="section"><a href="#creating-tags">Creating tags</a></span></dt><dt><span class="section"><a href="#browsing-revisions">Browsing revisions</a></span></dt><dt><span class="section"><a href="#generating-diffs">Generating diffs</a></span></dt><dt><span class="section"><a href="#viewing-old-file-versions">Viewing old file versions</a></span></dt><dt><span class="section"><a href="#history-examples">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#counting-commits-on-a-branch">Counting the number of commits on a branch</a></span></dt><dt><span class="section"><a href="#checking-for-equal-branches">Check whether two branches point at the same history</a></span></dt><dt><span class="section"><a href="#finding-tagged-descendants">Find first tagged version including a given fix</a></span></dt><dt><span class="section"><a href="#showing-commits-unique-to-a-branch">Showing commits unique to a given branch</a></span></dt><dt><span class="section"><a href="#making-a-release">Creating a changelog and tarball for a software release</a></span></dt><dt><span class="section"><a href="#Finding-commits-With-given-Content">Finding commits referencing a file with given content</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#Developing-With-git">3. Developing with Git</a></span></dt><dd><dl><dt><span class="section"><a href="#telling-git-your-name">Telling Git your name</a></span></dt><dt><span class="section"><a href="#creating-a-new-repository">Creating a new repository</a></span></dt><dt><span class="section"><a href="#how-to-make-a-commit">How to make a commit</a></span></dt><dt><span class="section"><a href="#creating-good-commit-messages">Creating good commit messages</a></span></dt><dt><span class="section"><a href="#ignoring-files">Ignoring files</a></span></dt><dt><span class="section"><a href="#how-to-merge">How to merge</a></span></dt><dt><span class="section"><a href="#resolving-a-merge">Resolving a merge</a></span></dt><dd><dl><dt><span class="section"><a href="#conflict-resolution">Getting conflict-resolution help during a merge</a></span></dt></dl></dd><dt><span class="section"><a href="#undoing-a-merge">Undoing a merge</a></span></dt><dt><span class="section"><a href="#fast-forwards">Fast-forward merges</a></span></dt><dt><span class="section"><a href="#fixing-mistakes">Fixing mistakes</a></span></dt><dd><dl><dt><span class="section"><a href="#reverting-a-commit">Fixing a mistake with a new commit</a></span></dt><dt><span class="section"><a href="#fixing-a-mistake-by-rewriting-history">Fixing a mistake by rewriting history</a></span></dt><dt><span class="section"><a href="#checkout-of-path">Checking out an old version of a file</a></span></dt><dt><span class="section"><a href="#interrupted-work">Temporarily setting aside work in progress</a></span></dt></dl></dd><dt><span class="section"><a href="#ensuring-good-performance">Ensuring good performance</a></span></dt><dt><span class="section"><a href="#ensuring-reliability">Ensuring reliability</a></span></dt><dd><dl><dt><span class="section"><a href="#checking-for-corruption">Checking the repository for corruption</a></span></dt><dt><span class="section"><a href="#recovering-lost-changes">Recovering lost changes</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#sharing-development">4. Sharing development with others</a></span></dt><dd><dl><dt><span class="section"><a href="#getting-updates-With-git-pull">Getting updates with git pull</a></span></dt><dt><span class="section"><a href="#submitting-patches">Submitting patches to a project</a></span></dt><dt><span class="section"><a href="#importing-patches">Importing patches to a project</a></span></dt><dt><span class="section"><a href="#public-repositories">Public Git repositories</a></span></dt><dd><dl><dt><span class="section"><a href="#setting-up-a-public-repository">Setting up a public repository</a></span></dt><dt><span class="section"><a href="#exporting-via-git">Exporting a Git repository via the Git protocol</a></span></dt><dt><span class="section"><a href="#exporting-via-http">Exporting a git repository via HTTP</a></span></dt><dt><span class="section"><a href="#pushing-changes-to-a-public-repository">Pushing changes to a public repository</a></span></dt><dt><span class="section"><a href="#forcing-push">What to do when a push fails</a></span></dt><dt><span class="section"><a href="#setting-up-a-shared-repository">Setting up a shared repository</a></span></dt><dt><span class="section"><a href="#setting-up-gitweb">Allowing web browsing of a repository</a></span></dt></dl></dd><dt><span class="section"><a href="#how-to-get-a-git-repository-with-minimal-history">How to get a Git repository with minimal history</a></span></dt><dt><span class="section"><a href="#sharing-development-examples">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#maintaining-topic-branches">Maintaining topic branches for a Linux subsystem maintainer</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#cleaning-up-history">5. Rewriting history and maintaining patch series</a></span></dt><dd><dl><dt><span class="section"><a href="#patch-series">Creating the perfect patch series</a></span></dt><dt><span class="section"><a href="#using-git-rebase">Keeping a patch series up to date using git rebase</a></span></dt><dt><span class="section"><a href="#rewriting-one-commit">Rewriting a single commit</a></span></dt><dt><span class="section"><a href="#reordering-patch-series">Reordering or selecting from a patch series</a></span></dt><dt><span class="section"><a href="#interactive-rebase">Using interactive rebases</a></span></dt><dt><span class="section"><a href="#patch-series-tools">Other tools</a></span></dt><dt><span class="section"><a href="#problems-With-rewriting-history">Problems with rewriting history</a></span></dt><dt><span class="section"><a href="#bisect-merges">Why bisecting merge commits can be harder than bisecting linear history</a></span></dt></dl></dd><dt><span class="chapter"><a href="#advanced-branch-management">6. Advanced branch management</a></span></dt><dd><dl><dt><span class="section"><a href="#fetching-individual-branches">Fetching individual branches</a></span></dt><dt><span class="section"><a href="#fetch-fast-forwards">git fetch and fast-forwards</a></span></dt><dt><span class="section"><a href="#forcing-fetch">Forcing git fetch to do non-fast-forward updates</a></span></dt><dt><span class="section"><a href="#remote-branch-configuration">Configuring remote-tracking branches</a></span></dt></dl></dd><dt><span class="chapter"><a href="#git-concepts">7. Git concepts</a></span></dt><dd><dl><dt><span class="section"><a href="#the-object-database">The Object Database</a></span></dt><dd><dl><dt><span class="section"><a href="#commit-object">Commit Object</a></span></dt><dt><span class="section"><a href="#tree-object">Tree Object</a></span></dt><dt><span class="section"><a href="#blob-object">Blob Object</a></span></dt><dt><span class="section"><a href="#trust">Trust</a></span></dt><dt><span class="section"><a href="#tag-object">Tag Object</a></span></dt><dt><span class="section"><a href="#pack-files">How Git stores objects efficiently: pack files</a></span></dt><dt><span class="section"><a href="#dangling-objects">Dangling objects</a></span></dt><dt><span class="section"><a href="#recovering-from-repository-corruption">Recovering from repository corruption</a></span></dt></dl></dd><dt><span class="section"><a href="#the-index">The index</a></span></dt></dl></dd><dt><span class="chapter"><a href="#submodules">8. Submodules</a></span></dt><dd><dl><dt><span class="section"><a href="#pitfalls-with-submodules">Pitfalls with submodules</a></span></dt></dl></dd><dt><span class="chapter"><a href="#low-level-operations">9. Low-level Git operations</a></span></dt><dd><dl><dt><span class="section"><a href="#object-manipulation">Object access and manipulation</a></span></dt><dt><span class="section"><a href="#the-workflow">The Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#working-directory-to-index">working directory → index</a></span></dt><dt><span class="section"><a href="#index-to-object-database">index → object database</a></span></dt><dt><span class="section"><a href="#object-database-to-index">object database → index</a></span></dt><dt><span class="section"><a href="#index-to-working-directory">index → working directory</a></span></dt><dt><span class="section"><a href="#tying-it-all-together">Tying it all together</a></span></dt></dl></dd><dt><span class="section"><a href="#examining-the-data">Examining the data</a></span></dt><dt><span class="section"><a href="#merging-multiple-trees">Merging multiple trees</a></span></dt><dt><span class="section"><a href="#merging-multiple-trees-2">Merging multiple trees, continued</a></span></dt></dl></dd><dt><span class="chapter"><a href="#hacking-git">10. Hacking Git</a></span></dt><dd><dl><dt><span class="section"><a href="#object-details">Object storage format</a></span></dt><dt><span class="section"><a href="#birdview-on-the-source-code">A birds-eye view of Git’s source code</a></span></dt></dl></dd><dt><span class="chapter"><a href="#glossary">11. Git Glossary</a></span></dt><dd><dl><dt><span class="section"><a href="#git-explained">Git explained</a></span></dt></dl></dd><dt><span class="appendix"><a href="#git-quick-start">A. Git Quick Reference</a></span></dt><dd><dl><dt><span class="section"><a href="#quick-creating-a-new-repository">Creating a new repository</a></span></dt><dt><span class="section"><a href="#managing-branches">Managing branches</a></span></dt><dt><span class="section"><a href="#exploring-history">Exploring history</a></span></dt><dt><span class="section"><a href="#making-changes">Making changes</a></span></dt><dt><span class="section"><a href="#merging">Merging</a></span></dt><dt><span class="section"><a href="#sharing-your-changes">Sharing your changes</a></span></dt><dt><span class="section"><a href="#repository-maintenance">Repository maintenance</a></span></dt></dl></dd><dt><span class="appendix"><a href="#todo">B. Notes and todo list for this manual</a></span></dt><dd><dl><dt><span class="section"><a href="#todo-list">Todo list</a></span></dt></dl></dd></dl></div> | |
| <div class="preface"><div class="titlepage"><div><div><h1 class="title"><a name="_introduction"></a>Introduction</h1></div></div></div> | |
| <p>Git is a fast distributed revision control system.</p> | |
| <p>This manual is designed to be readable by someone with basic UNIX | |
| command-line skills, but no previous knowledge of Git.</p> | |
| <p><a class="xref" href="#repositories-and-branches" title="Chapter 1. Repositories and Branches">Chapter 1, <i>Repositories and Branches</i></a> and <a class="xref" href="#exploring-git-history" title="Chapter 2. Exploring Git history">Chapter 2, <i>Exploring Git history</i></a> explain how | |
| to fetch and study a project using git—read these chapters to learn how | |
| to build and test a particular version of a software project, search for | |
| regressions, and so on.</p> | |
| <p>People needing to do actual development will also want to read | |
| <a class="xref" href="#Developing-With-git" title="Chapter 3. Developing with Git">Chapter 3, <i>Developing with Git</i></a> and <a class="xref" href="#sharing-development" title="Chapter 4. Sharing development with others">Chapter 4, <i>Sharing development with others</i></a>.</p> | |
| <p>Further chapters cover more specialized topics.</p> | |
| <p>Comprehensive reference documentation is available through the man | |
| pages, or <a class="ulink" href="git-help.html" target="_top">git-help(1)</a> command. For example, for the command | |
| <code class="literal">git</code> <code class="literal">clone</code> <span class="emphasis"><em><repo></em></span>, you can either use:</p> | |
| <pre class="screen">$ man git-clone</pre> | |
| <p>or:</p> | |
| <pre class="screen">$ git help clone</pre> | |
| <p>With the latter, you can use the manual viewer of your choice; see | |
| <a class="ulink" href="git-help.html" target="_top">git-help(1)</a> for more information.</p> | |
| <p>See also <a class="xref" href="#git-quick-start" title="Appendix A. Git Quick Reference">Appendix A, <i>Git Quick Reference</i></a> for a brief overview of Git commands, | |
| without any explanation.</p> | |
| <p>Finally, see <a class="xref" href="#todo" title="Appendix B. Notes and todo list for this manual">Appendix B, <i>Notes and todo list for this manual</i></a> for ways that you can help make this manual more | |
| complete.</p> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="repositories-and-branches"></a>Chapter 1. Repositories and Branches</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#how-to-get-a-git-repository">How to get a Git repository</a></span></dt><dt><span class="section"><a href="#how-to-check-out">How to check out a different version of a project</a></span></dt><dt><span class="section"><a href="#understanding-commits">Understanding History: Commits</a></span></dt><dd><dl><dt><span class="section"><a href="#understanding-reachability">Understanding history: commits, parents, and reachability</a></span></dt><dt><span class="section"><a href="#history-diagrams">Understanding history: History diagrams</a></span></dt><dt><span class="section"><a href="#what-is-a-branch">Understanding history: What is a branch?</a></span></dt></dl></dd><dt><span class="section"><a href="#manipulating-branches">Manipulating branches</a></span></dt><dt><span class="section"><a href="#detached-head">Examining an old version without creating a new branch</a></span></dt><dt><span class="section"><a href="#examining-remote-branches">Examining branches from a remote repository</a></span></dt><dt><span class="section"><a href="#how-git-stores-references">Naming branches, tags, and other references</a></span></dt><dt><span class="section"><a href="#Updating-a-repository-With-git-fetch">Updating a repository with git fetch</a></span></dt><dt><span class="section"><a href="#fetching-branches">Fetching branches from other repositories</a></span></dt></dl></div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-to-get-a-git-repository"></a>How to get a Git repository</h2></div></div></div> | |
| <p>It will be useful to have a Git repository to experiment with as you | |
| read this manual.</p> | |
| <p>The best way to get one is by using the <a class="ulink" href="git-clone.html" target="_top">git-clone(1)</a> command to | |
| download a copy of an existing repository. If you don’t already have a | |
| project in mind, here are some interesting examples:</p> | |
| <pre class="screen"> # Git itself (approx. 40MB download): | |
| $ git clone git://git.kernel.org/pub/scm/git/git.git | |
| # the Linux kernel (approx. 640MB download): | |
| $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git</pre> | |
| <p>The initial clone may be time-consuming for a large project, but you | |
| will only need to clone once.</p> | |
| <p>The clone command creates a new directory named after the project | |
| (<code class="literal">git</code> or <code class="literal">linux</code> in the examples above). After you cd into this | |
| directory, you will see that it contains a copy of the project files, | |
| called the <a class="link" href="#def_working_tree">working tree</a>, together with a special | |
| top-level directory named .<code class="literal">git</code>, which contains all the information | |
| about the history of the project.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-to-check-out"></a>How to check out a different version of a project</h2></div></div></div> | |
| <p>Git is best thought of as a tool for storing the history of a collection | |
| of files. It stores the history as a compressed collection of | |
| interrelated snapshots of the project’s contents. In Git each such | |
| version is called a <a class="link" href="#def_commit">commit</a>.</p> | |
| <p>Those snapshots aren’t necessarily all arranged in a single line from | |
| oldest to newest; instead, work may simultaneously proceed along | |
| parallel lines of development, called <a class="link" href="#def_branch">branches</a>, which may | |
| merge and diverge.</p> | |
| <p>A single Git repository can track development on multiple branches. It | |
| does this by keeping a list of <a class="link" href="#def_head">heads</a> which reference the | |
| latest commit on each branch; the <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a> command shows | |
| you the list of branch heads:</p> | |
| <pre class="screen">$ git branch | |
| * master</pre> | |
| <p>A freshly cloned repository contains a single branch head, by default | |
| named "master", with the working directory initialized to the state of | |
| the project referred to by that branch head.</p> | |
| <p>Most projects also use <a class="link" href="#def_tag">tags</a>. Tags, like heads, are | |
| references into the project’s history, and can be listed using the | |
| <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> command:</p> | |
| <pre class="screen">$ git tag -l | |
| v2.6.11 | |
| v2.6.11-tree | |
| v2.6.12 | |
| v2.6.12-rc2 | |
| v2.6.12-rc3 | |
| v2.6.12-rc4 | |
| v2.6.12-rc5 | |
| v2.6.12-rc6 | |
| v2.6.13 | |
| ...</pre> | |
| <p>Tags are expected to always point at the same version of a project, | |
| while heads are expected to advance as development progresses.</p> | |
| <p>Create a new branch head pointing to one of these versions and check it | |
| out using <a class="ulink" href="git-switch.html" target="_top">git-switch(1)</a>:</p> | |
| <pre class="screen">$ git switch -c new v2.6.13</pre> | |
| <p>The working directory then reflects the contents that the project had | |
| when it was tagged v2.6.13, and <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a> shows two | |
| branches, with an asterisk marking the currently checked-out branch:</p> | |
| <pre class="screen">$ git branch | |
| master | |
| * new</pre> | |
| <p>If you decide that you’d rather see version 2.6.17, you can modify | |
| the current branch to point at v2.6.17 instead, with</p> | |
| <pre class="screen">$ git reset --hard v2.6.17</pre> | |
| <p>Note that if the current branch head was your only reference to a | |
| particular point in history, then resetting that branch may leave you | |
| with no way to find the history it used to point to; so use this command | |
| carefully.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="understanding-commits"></a>Understanding History: Commits</h2></div></div></div> | |
| <p>Every change in the history of a project is represented by a commit. | |
| The <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> command shows the most recent commit on the | |
| current branch:</p> | |
| <pre class="screen">$ git show | |
| commit 17cf781661e6d38f737f15f53ab552f1e95960d7 | |
| Author: Linus Torvalds <torvalds@ppc970.osdl.org.(none)> | |
| Date: Tue Apr 19 14:11:06 2005 -0700 | |
| Remove duplicate getenv(DB_ENVIRONMENT) call | |
| Noted by Tony Luck. | |
| diff --git a/init-db.c b/init-db.c | |
| index 65898fa..b002dc6 100644 | |
| --- a/init-db.c | |
| +++ b/init-db.c | |
| @@ -7,7 +7,7 @@ | |
| int main(int argc, char **argv) | |
| { | |
| - char *sha1_dir = getenv(DB_ENVIRONMENT), *path; | |
| + char *sha1_dir, *path; | |
| int len, i; | |
| if (mkdir(".git", 0755) < 0) {</pre> | |
| <p>As you can see, a commit shows who made the latest change, what they | |
| did, and why.</p> | |
| <p>Every commit has a 40-hexdigit id, sometimes called the "object name" or the | |
| "SHA-1 id", shown on the first line of the <code class="literal">git</code> <code class="literal">show</code> output. You can usually | |
| refer to a commit by a shorter name, such as a tag or a branch name, but this | |
| longer name can also be useful. Most importantly, it is a globally unique | |
| name for this commit: so if you tell somebody else the object name (for | |
| example in email), then you are guaranteed that name will refer to the same | |
| commit in their repository that it does in yours (assuming their repository | |
| has that commit at all). Since the object name is computed as a hash over the | |
| contents of the commit, you are guaranteed that the commit can never change | |
| without its name also changing.</p> | |
| <p>In fact, in <a class="xref" href="#git-concepts" title="Chapter 7. Git concepts">Chapter 7, <i>Git concepts</i></a> we shall see that everything stored in Git | |
| history, including file data and directory contents, is stored in an object | |
| with a name that is a hash of its contents.</p> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="understanding-reachability"></a>Understanding history: commits, parents, and reachability</h3></div></div></div> | |
| <p>Every commit (except the very first commit in a project) also has a | |
| parent commit which shows what happened before this commit. | |
| Following the chain of parents will eventually take you back to the | |
| beginning of the project.</p> | |
| <p>However, the commits do not form a simple list; Git allows lines of | |
| development to diverge and then reconverge, and the point where two | |
| lines of development reconverge is called a "merge". The commit | |
| representing a merge can therefore have more than one parent, with | |
| each parent representing the most recent commit on one of the lines | |
| of development leading to that point.</p> | |
| <p>The best way to see how this works is using the <a class="ulink" href="gitk.html" target="_top">gitk(1)</a> | |
| command; running gitk now on a Git repository and looking for merge | |
| commits will help understand how Git organizes history.</p> | |
| <p>In the following, we say that commit X is "reachable" from commit Y | |
| if commit X is an ancestor of commit Y. Equivalently, you could say | |
| that Y is a descendant of X, or that there is a chain of parents | |
| leading from commit Y to commit X.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="history-diagrams"></a>Understanding history: History diagrams</h3></div></div></div> | |
| <p>We will sometimes represent Git history using diagrams like the one | |
| below. Commits are shown as "o", and the links between them with | |
| lines drawn with - / and \. Time goes left to right:</p> | |
| <pre class="literallayout"> o--o--o <-- Branch A | |
| / | |
| o--o--o <-- master | |
| \ | |
| o--o--o <-- Branch B</pre> | |
| <p>If we need to talk about a particular commit, the character "o" may | |
| be replaced with another letter or number.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="what-is-a-branch"></a>Understanding history: What is a branch?</h3></div></div></div> | |
| <p>When we need to be precise, we will use the word "branch" to mean a line | |
| of development, and "branch head" (or just "head") to mean a reference | |
| to the most recent commit on a branch. In the example above, the branch | |
| head named "A" is a pointer to one particular commit, but we refer to | |
| the line of three commits leading up to that point as all being part of | |
| "branch A".</p> | |
| <p>However, when no confusion will result, we often just use the term | |
| "branch" both for branches and for branch heads.</p> | |
| </div> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="manipulating-branches"></a>Manipulating branches</h2></div></div></div> | |
| <p>Creating, deleting, and modifying branches is quick and easy; here’s | |
| a summary of the commands:</p> | |
| <div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">git</code> <code class="literal">branch</code></span></dt><dd> | |
| list all branches. | |
| </dd><dt><span class="term"><code class="literal">git</code> <code class="literal">branch</code> <span class="emphasis"><em><branch></em></span></span></dt><dd> | |
| create a new branch named <span class="emphasis"><em><branch></em></span>, referencing the same | |
| point in history as the current branch. | |
| </dd><dt><span class="term"><code class="literal">git</code> <code class="literal">branch</code> <span class="emphasis"><em><branch></em></span> <span class="emphasis"><em><start-point></em></span></span></dt><dd> | |
| create a new branch named <span class="emphasis"><em><branch></em></span>, referencing | |
| <span class="emphasis"><em><start-point></em></span>, which may be specified any way you like, | |
| including using a branch name or a tag name. | |
| </dd><dt><span class="term"><code class="literal">git</code> <code class="literal">branch</code> <code class="literal">-d</code> <span class="emphasis"><em><branch></em></span></span></dt><dd> | |
| delete the branch <span class="emphasis"><em><branch></em></span>; if the branch is not fully | |
| merged in its upstream branch or contained in the current branch, | |
| this command will fail with a warning. | |
| </dd><dt><span class="term"><code class="literal">git</code> <code class="literal">branch</code> <code class="literal">-D</code> <span class="emphasis"><em><branch></em></span></span></dt><dd> | |
| delete the branch <span class="emphasis"><em><branch></em></span> irrespective of its merged status. | |
| </dd><dt><span class="term"><code class="literal">git</code> <code class="literal">switch</code> <span class="emphasis"><em><branch></em></span></span></dt><dd> | |
| make the current branch <span class="emphasis"><em><branch></em></span>, updating the working | |
| directory to reflect the version referenced by <span class="emphasis"><em><branch></em></span>. | |
| </dd><dt><span class="term"><code class="literal">git</code> <code class="literal">switch</code> <code class="literal">-c</code> <span class="emphasis"><em><new></em></span> <span class="emphasis"><em><start-point></em></span></span></dt><dd> | |
| create a new branch <span class="emphasis"><em><new></em></span> referencing <span class="emphasis"><em><start-point></em></span>, and | |
| check it out. | |
| </dd></dl></div> | |
| <p>The special symbol "HEAD" can always be used to refer to the current | |
| branch. In fact, Git uses a file named <code class="literal">HEAD</code> in the .<code class="literal">git</code> directory | |
| to remember which branch is current:</p> | |
| <pre class="screen">$ cat .git/HEAD | |
| ref: refs/heads/master</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="detached-head"></a>Examining an old version without creating a new branch</h2></div></div></div> | |
| <p>The <code class="literal">git</code> <code class="literal">switch</code> command normally expects a branch head, but will also | |
| accept an arbitrary commit when invoked with --detach; for example, | |
| you can check out the commit referenced by a tag:</p> | |
| <pre class="screen">$ git switch --detach v2.6.17 | |
| Note: checking out 'v2.6.17'. | |
| You are in 'detached HEAD' state. You can look around, make experimental | |
| changes and commit them, and you can discard any commits you make in this | |
| state without impacting any branches by performing another switch. | |
| If you want to create a new branch to retain commits you create, you may | |
| do so (now or later) by using -c with the switch command again. Example: | |
| git switch -c new_branch_name | |
| HEAD is now at 427abfa Linux v2.6.17</pre> | |
| <p>The HEAD then refers to the SHA-1 of the commit instead of to a branch, | |
| and git branch shows that you are no longer on a branch:</p> | |
| <pre class="screen">$ cat .git/HEAD | |
| 427abfa28afedffadfca9dd8b067eb6d36bac53f | |
| $ git branch | |
| * (detached from v2.6.17) | |
| master</pre> | |
| <p>In this case we say that the HEAD is "detached".</p> | |
| <p>This is an easy way to check out a particular version without having to | |
| make up a name for the new branch. You can still create a new branch | |
| (or tag) for this version later if you decide to.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="examining-remote-branches"></a>Examining branches from a remote repository</h2></div></div></div> | |
| <p>The "master" branch that was created at the time you cloned is a copy | |
| of the HEAD in the repository that you cloned from. That repository | |
| may also have had other branches, though, and your local repository | |
| keeps branches which track each of those remote branches, called | |
| remote-tracking branches, which you | |
| can view using the <code class="literal">-r</code> option to <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a>:</p> | |
| <pre class="screen">$ git branch -r | |
| origin/HEAD | |
| origin/html | |
| origin/maint | |
| origin/man | |
| origin/master | |
| origin/next | |
| origin/seen | |
| origin/todo</pre> | |
| <p>In this example, "origin" is called a remote repository, or "remote" | |
| for short. The branches of this repository are called "remote | |
| branches" from our point of view. The remote-tracking branches listed | |
| above were created based on the remote branches at clone time and will | |
| be updated by <code class="literal">git</code> <code class="literal">fetch</code> (hence <code class="literal">git</code> <code class="literal">pull</code>) and <code class="literal">git</code> <code class="literal">push</code>. See | |
| <a class="xref" href="#Updating-a-repository-With-git-fetch" title="Updating a repository with git fetch">the section called “Updating a repository with git fetch”</a> for details.</p> | |
| <p>You might want to build on one of these remote-tracking branches | |
| on a branch of your own, just as you would for a tag:</p> | |
| <pre class="screen">$ git switch -c my-todo-copy origin/todo</pre> | |
| <p>You can also check out <code class="literal">origin/todo</code> directly to examine it or | |
| write a one-off patch. See <a class="link" href="#detached-head" title="Examining an old version without creating a new branch">detached head</a>.</p> | |
| <p>Note that the name "origin" is just the name that Git uses by default | |
| to refer to the repository that you cloned from.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-git-stores-references"></a>Naming branches, tags, and other references</h2></div></div></div> | |
| <p>Branches, remote-tracking branches, and tags are all references to | |
| commits. All references are named with a slash-separated path name | |
| starting with <code class="literal">refs</code>; the names we’ve been using so far are actually | |
| shorthand:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| The branch <code class="literal">test</code> is short for <code class="literal">refs/heads/test</code>. | |
| </li><li class="listitem"> | |
| The tag <code class="literal">v2.6.18</code> is short for <code class="literal">refs/tags/v2.6.18</code>. | |
| </li><li class="listitem"> | |
| <code class="literal">origin/master</code> is short for <code class="literal">refs/remotes/origin/master</code>. | |
| </li></ul></div> | |
| <p>The full name is occasionally useful if, for example, there ever | |
| exists a tag and a branch with the same name.</p> | |
| <p>(Newly created refs are actually stored in the .<code class="literal">git/refs</code> directory, | |
| under the path given by their name. However, for efficiency reasons | |
| they may also be packed together in a single file; see | |
| <a class="ulink" href="git-pack-refs.html" target="_top">git-pack-refs(1)</a>).</p> | |
| <p>As another useful shortcut, the "HEAD" of a repository can be referred | |
| to just using the name of that repository. So, for example, "origin" | |
| is usually a shortcut for the HEAD branch in the repository "origin".</p> | |
| <p>For the complete list of paths which Git checks for references, and | |
| the order it uses to decide which to choose when there are multiple | |
| references with the same shorthand name, see the "SPECIFYING | |
| REVISIONS" section of <a class="ulink" href="gitrevisions.html" target="_top">gitrevisions(7)</a>.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="Updating-a-repository-With-git-fetch"></a>Updating a repository with git fetch</h2></div></div></div> | |
| <p>After you clone a repository and commit a few changes of your own, you | |
| may wish to check the original repository for updates.</p> | |
| <p>The <code class="literal">git-fetch</code> command, with no arguments, will update all of the | |
| remote-tracking branches to the latest version found in the original | |
| repository. It will not touch any of your own branches—not even the | |
| "master" branch that was created for you on clone.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fetching-branches"></a>Fetching branches from other repositories</h2></div></div></div> | |
| <p>You can also track branches from repositories other than the one you | |
| cloned from, using <a class="ulink" href="git-remote.html" target="_top">git-remote(1)</a>:</p> | |
| <pre class="screen">$ git remote add staging git://git.kernel.org/.../gregkh/staging.git | |
| $ git fetch staging | |
| ... | |
| From git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging | |
| * [new branch] master -> staging/master | |
| * [new branch] staging-linus -> staging/staging-linus | |
| * [new branch] staging-next -> staging/staging-next</pre> | |
| <p>New remote-tracking branches will be stored under the shorthand name | |
| that you gave <code class="literal">git</code> <code class="literal">remote</code> <code class="literal">add</code>, in this case <code class="literal">staging</code>:</p> | |
| <pre class="screen">$ git branch -r | |
| origin/HEAD -> origin/master | |
| origin/master | |
| staging/master | |
| staging/staging-linus | |
| staging/staging-next</pre> | |
| <p>If you run <code class="literal">git</code> <code class="literal">fetch</code> <span class="emphasis"><em><remote></em></span> later, the remote-tracking branches | |
| for the named <span class="emphasis"><em><remote></em></span> will be updated.</p> | |
| <p>If you examine the file .<code class="literal">git/config</code>, you will see that Git has added | |
| a new stanza:</p> | |
| <pre class="screen">$ cat .git/config | |
| ... | |
| [remote "staging"] | |
| url = git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git | |
| fetch = +refs/heads/*:refs/remotes/staging/* | |
| ...</pre> | |
| <p>This is what causes Git to track the remote’s branches; you may modify | |
| or delete these configuration options by editing .<code class="literal">git/config</code> with a | |
| text editor. (See the "CONFIGURATION FILE" section of | |
| <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for details.)</p> | |
| </div> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="exploring-git-history"></a>Chapter 2. Exploring Git history</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#using-bisect">How to use bisect to find a regression</a></span></dt><dt><span class="section"><a href="#naming-commits">Naming commits</a></span></dt><dt><span class="section"><a href="#creating-tags">Creating tags</a></span></dt><dt><span class="section"><a href="#browsing-revisions">Browsing revisions</a></span></dt><dt><span class="section"><a href="#generating-diffs">Generating diffs</a></span></dt><dt><span class="section"><a href="#viewing-old-file-versions">Viewing old file versions</a></span></dt><dt><span class="section"><a href="#history-examples">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#counting-commits-on-a-branch">Counting the number of commits on a branch</a></span></dt><dt><span class="section"><a href="#checking-for-equal-branches">Check whether two branches point at the same history</a></span></dt><dt><span class="section"><a href="#finding-tagged-descendants">Find first tagged version including a given fix</a></span></dt><dt><span class="section"><a href="#showing-commits-unique-to-a-branch">Showing commits unique to a given branch</a></span></dt><dt><span class="section"><a href="#making-a-release">Creating a changelog and tarball for a software release</a></span></dt><dt><span class="section"><a href="#Finding-commits-With-given-Content">Finding commits referencing a file with given content</a></span></dt></dl></dd></dl></div> | |
| <p>Git is best thought of as a tool for storing the history of a | |
| collection of files. It does this by storing compressed snapshots of | |
| the contents of a file hierarchy, together with "commits" which show | |
| the relationships between these snapshots.</p> | |
| <p>Git provides extremely flexible and fast tools for exploring the | |
| history of a project.</p> | |
| <p>We start with one specialized tool that is useful for finding the | |
| commit that introduced a bug into a project.</p> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="using-bisect"></a>How to use bisect to find a regression</h2></div></div></div> | |
| <p>Suppose version 2.6.18 of your project worked, but the version at | |
| "master" crashes. Sometimes the best way to find the cause of such a | |
| regression is to perform a brute-force search through the project’s | |
| history to find the particular commit that caused the problem. The | |
| <a class="ulink" href="git-bisect.html" target="_top">git-bisect(1)</a> command can help you do this:</p> | |
| <pre class="screen">$ git bisect start | |
| $ git bisect good v2.6.18 | |
| $ git bisect bad master | |
| Bisecting: 3537 revisions left to test after this | |
| [65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]</pre> | |
| <p>If you run <code class="literal">git</code> <code class="literal">branch</code> at this point, you’ll see that Git has | |
| temporarily moved you in "(no branch)". HEAD is now detached from any | |
| branch and points directly to a commit (with commit id 65934) that | |
| is reachable from "master" but not from v2.6.18. Compile and test it, | |
| and see whether it crashes. Assume it does crash. Then:</p> | |
| <pre class="screen">$ git bisect bad | |
| Bisecting: 1769 revisions left to test after this | |
| [7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings</pre> | |
| <p>checks out an older version. Continue like this, telling Git at each | |
| stage whether the version it gives you is good or bad, and notice | |
| that the number of revisions left to test is cut approximately in | |
| half each time.</p> | |
| <p>After about 13 tests (in this case), it will output the commit id of | |
| the guilty commit. You can then examine the commit with | |
| <a class="ulink" href="git-show.html" target="_top">git-show(1)</a>, find out who wrote it, and mail them your bug | |
| report with the commit id. Finally, run</p> | |
| <pre class="screen">$ git bisect reset</pre> | |
| <p>to return you to the branch you were on before.</p> | |
| <p>Note that the version which <code class="literal">git</code> <code class="literal">bisect</code> checks out for you at each | |
| point is just a suggestion, and you’re free to try a different | |
| version if you think it would be a good idea. For example, | |
| occasionally you may land on a commit that broke something unrelated; | |
| run</p> | |
| <pre class="screen">$ git bisect visualize</pre> | |
| <p>which will run gitk and label the commit it chose with a marker that | |
| says "bisect". Choose a safe-looking commit nearby, note its commit | |
| id, and check it out with:</p> | |
| <pre class="screen">$ git reset --hard fb47ddb2db</pre> | |
| <p>then test, run <code class="literal">bisect</code> <code class="literal">good</code> or <code class="literal">bisect</code> <code class="literal">bad</code> as appropriate, and | |
| continue.</p> | |
| <p>Instead of <code class="literal">git</code> <code class="literal">bisect</code> <code class="literal">visualize</code> and then <code class="literal">git</code> <code class="literal">reset</code> <code class="literal">--hard</code> | |
| <code class="literal">fb47ddb2db</code>, you might just want to tell Git that you want to skip | |
| the current commit:</p> | |
| <pre class="screen">$ git bisect skip</pre> | |
| <p>In this case, though, Git may not eventually be able to tell the first | |
| bad one between some first skipped commits and a later bad commit.</p> | |
| <p>There are also ways to automate the bisecting process if you have a | |
| test script that can tell a good from a bad commit. See | |
| <a class="ulink" href="git-bisect.html" target="_top">git-bisect(1)</a> for more information about this and other <code class="literal">git</code> | |
| <code class="literal">bisect</code> features.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="naming-commits"></a>Naming commits</h2></div></div></div> | |
| <p>We have seen several ways of naming commits already:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| 40-hexdigit object name | |
| </li><li class="listitem"> | |
| branch name: refers to the commit at the head of the given | |
| branch | |
| </li><li class="listitem"> | |
| tag name: refers to the commit pointed to by the given tag | |
| (we’ve seen branches and tags are special cases of | |
| <a class="link" href="#how-git-stores-references" title="Naming branches, tags, and other references">references</a>). | |
| </li><li class="listitem"> | |
| HEAD: refers to the head of the current branch | |
| </li></ul></div> | |
| <p>There are many more; see the "SPECIFYING REVISIONS" section of the | |
| <a class="ulink" href="gitrevisions.html" target="_top">gitrevisions(7)</a> man page for the complete list of ways to | |
| name revisions. Some examples:</p> | |
| <pre class="screen">$ git show fb47ddb2 # the first few characters of the object name | |
| # are usually enough to specify it uniquely | |
| $ git show HEAD^ # the parent of the HEAD commit | |
| $ git show HEAD^^ # the grandparent | |
| $ git show HEAD~4 # the great-great-grandparent</pre> | |
| <p>Recall that merge commits may have more than one parent; by default, | |
| <code class="literal">^</code> and <code class="literal">~</code> follow the first parent listed in the commit, but you can | |
| also choose:</p> | |
| <pre class="screen">$ git show HEAD^1 # show the first parent of HEAD | |
| $ git show HEAD^2 # show the second parent of HEAD</pre> | |
| <p>In addition to HEAD, there are several other special names for | |
| commits:</p> | |
| <p>Merges (to be discussed later), as well as operations such as | |
| <code class="literal">git</code> <code class="literal">reset</code>, which change the currently checked-out commit, generally | |
| set ORIG_HEAD to the value HEAD had before the current operation.</p> | |
| <p>The <code class="literal">git</code> <code class="literal">fetch</code> operation always stores the head of the last fetched | |
| branch in FETCH_HEAD. For example, if you run <code class="literal">git</code> <code class="literal">fetch</code> without | |
| specifying a local branch as the target of the operation</p> | |
| <pre class="screen">$ git fetch git://example.com/proj.git theirbranch</pre> | |
| <p>the fetched commits will still be available from FETCH_HEAD.</p> | |
| <p>When we discuss merges we’ll also see the special name MERGE_HEAD, | |
| which refers to the other branch that we’re merging in to the current | |
| branch.</p> | |
| <p>The <a class="ulink" href="git-rev-parse.html" target="_top">git-rev-parse(1)</a> command is a low-level command that is | |
| occasionally useful for translating some name for a commit to the object | |
| name for that commit:</p> | |
| <pre class="screen">$ git rev-parse origin | |
| e05db0fd4f31dde7005f075a84f96b360d05984b</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="creating-tags"></a>Creating tags</h2></div></div></div> | |
| <p>We can also create a tag to refer to a particular commit; after | |
| running</p> | |
| <pre class="screen">$ git tag stable-1 1b2e1d63ff</pre> | |
| <p>You can use <code class="literal">stable-1</code> to refer to the commit 1b2e1d63ff.</p> | |
| <p>This creates a "lightweight" tag. If you would also like to include a | |
| comment with the tag, and possibly sign it cryptographically, then you | |
| should create a tag object instead; see the <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> man page | |
| for details.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="browsing-revisions"></a>Browsing revisions</h2></div></div></div> | |
| <p>The <a class="ulink" href="git-log.html" target="_top">git-log(1)</a> command can show lists of commits. On its | |
| own, it shows all commits reachable from the parent commit; but you | |
| can also make more specific requests:</p> | |
| <pre class="screen">$ git log v2.5.. # commits since (not reachable from) v2.5 | |
| $ git log test..master # commits reachable from master but not test | |
| $ git log master..test # ...reachable from test but not master | |
| $ git log master...test # ...reachable from either test or master, | |
| # but not both | |
| $ git log --since="2 weeks ago" # commits from the last 2 weeks | |
| $ git log Makefile # commits which modify Makefile | |
| $ git log fs/ # ... which modify any file under fs/ | |
| $ git log -S'foo()' # commits which add or remove any file data | |
| # matching the string 'foo()'</pre> | |
| <p>And of course you can combine all of these; the following finds | |
| commits since v2.5 which touch the <code class="literal">Makefile</code> or any file under <code class="literal">fs</code>:</p> | |
| <pre class="screen">$ git log v2.5.. Makefile fs/</pre> | |
| <p>You can also ask git log to show patches:</p> | |
| <pre class="screen">$ git log -p</pre> | |
| <p>See the <code class="literal">--pretty</code> option in the <a class="ulink" href="git-log.html" target="_top">git-log(1)</a> man page for more | |
| display options.</p> | |
| <p>Note that git log starts with the most recent commit and works | |
| backwards through the parents; however, since Git history can contain | |
| multiple independent lines of development, the particular order that | |
| commits are listed in may be somewhat arbitrary.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="generating-diffs"></a>Generating diffs</h2></div></div></div> | |
| <p>You can generate diffs between any two versions using | |
| <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a>:</p> | |
| <pre class="screen">$ git diff master..test</pre> | |
| <p>That will produce the diff between the tips of the two branches. If | |
| you’d prefer to find the diff from their common ancestor to test, you | |
| can use three dots instead of two:</p> | |
| <pre class="screen">$ git diff master...test</pre> | |
| <p>Sometimes what you want instead is a set of patches; for this you can | |
| use <a class="ulink" href="git-format-patch.html" target="_top">git-format-patch(1)</a>:</p> | |
| <pre class="screen">$ git format-patch master..test</pre> | |
| <p>will generate a file with a patch for each commit reachable from test | |
| but not from master.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="viewing-old-file-versions"></a>Viewing old file versions</h2></div></div></div> | |
| <p>You can always view an old version of a file by just checking out the | |
| correct revision first. But sometimes it is more convenient to be | |
| able to view an old version of a single file without checking | |
| anything out; this command does that:</p> | |
| <pre class="screen">$ git show v2.5:fs/locks.c</pre> | |
| <p>Before the colon may be anything that names a commit, and after it | |
| may be any path to a file tracked by Git.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="history-examples"></a>Examples</h2></div></div></div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="counting-commits-on-a-branch"></a>Counting the number of commits on a branch</h3></div></div></div> | |
| <p>Suppose you want to know how many commits you’ve made on <code class="literal">mybranch</code> | |
| since it diverged from <code class="literal">origin</code>:</p> | |
| <pre class="screen">$ git log --pretty=oneline origin..mybranch | wc -l</pre> | |
| <p>Alternatively, you may often see this sort of thing done with the | |
| lower-level command <a class="ulink" href="git-rev-list.html" target="_top">git-rev-list(1)</a>, which just lists the SHA-1’s | |
| of all the given commits:</p> | |
| <pre class="screen">$ git rev-list origin..mybranch | wc -l</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="checking-for-equal-branches"></a>Check whether two branches point at the same history</h3></div></div></div> | |
| <p>Suppose you want to check whether two branches point at the same point | |
| in history.</p> | |
| <pre class="screen">$ git diff origin..master</pre> | |
| <p>will tell you whether the contents of the project are the same at the | |
| two branches; in theory, however, it’s possible that the same project | |
| contents could have been arrived at by two different historical | |
| routes. You could compare the object names:</p> | |
| <pre class="screen">$ git rev-list origin | |
| e05db0fd4f31dde7005f075a84f96b360d05984b | |
| $ git rev-list master | |
| e05db0fd4f31dde7005f075a84f96b360d05984b</pre> | |
| <p>Or you could recall that the <code class="literal">...</code> operator selects all commits | |
| reachable from either one reference or the other but not | |
| both; so</p> | |
| <pre class="screen">$ git log origin...master</pre> | |
| <p>will return no commits when the two branches are equal.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="finding-tagged-descendants"></a>Find first tagged version including a given fix</h3></div></div></div> | |
| <p>Suppose you know that the commit e05db0fd fixed a certain problem. | |
| You’d like to find the earliest tagged release that contains that | |
| fix.</p> | |
| <p>Of course, there may be more than one answer—if the history branched | |
| after commit e05db0fd, then there could be multiple "earliest" tagged | |
| releases.</p> | |
| <p>You could just visually inspect the commits since e05db0fd:</p> | |
| <pre class="screen">$ gitk e05db0fd..</pre> | |
| <p>or you can use <a class="ulink" href="git-name-rev.html" target="_top">git-name-rev(1)</a>, which will give the commit a | |
| name based on any tag it finds pointing to one of the commit’s | |
| descendants:</p> | |
| <pre class="screen">$ git name-rev --tags e05db0fd | |
| e05db0fd tags/v1.5.0-rc1^0~23</pre> | |
| <p>The <a class="ulink" href="git-describe.html" target="_top">git-describe(1)</a> command does the opposite, naming the | |
| revision using a tag on which the given commit is based:</p> | |
| <pre class="screen">$ git describe e05db0fd | |
| v1.5.0-rc0-260-ge05db0f</pre> | |
| <p>but that may sometimes help you guess which tags might come after the | |
| given commit.</p> | |
| <p>If you just want to verify whether a given tagged version contains a | |
| given commit, you could use <a class="ulink" href="git-merge-base.html" target="_top">git-merge-base(1)</a>:</p> | |
| <pre class="screen">$ git merge-base e05db0fd v1.5.0-rc1 | |
| e05db0fd4f31dde7005f075a84f96b360d05984b</pre> | |
| <p>The merge-base command finds a common ancestor of the given commits, | |
| and always returns one or the other in the case where one is a | |
| descendant of the other; so the above output shows that e05db0fd | |
| actually is an ancestor of v1.5.0-rc1.</p> | |
| <p>Alternatively, note that</p> | |
| <pre class="screen">$ git log v1.5.0-rc1..e05db0fd</pre> | |
| <p>will produce empty output if and only if v1.5.0-rc1 includes e05db0fd, | |
| because it outputs only commits that are not reachable from v1.5.0-rc1.</p> | |
| <p>As yet another alternative, the <a class="ulink" href="git-show-branch.html" target="_top">git-show-branch(1)</a> command lists | |
| the commits reachable from its arguments with a display on the left-hand | |
| side that indicates which arguments that commit is reachable from. | |
| So, if you run something like</p> | |
| <pre class="screen">$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2 | |
| ! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if | |
| available | |
| ! [v1.5.0-rc0] GIT v1.5.0 preview | |
| ! [v1.5.0-rc1] GIT v1.5.0-rc1 | |
| ! [v1.5.0-rc2] GIT v1.5.0-rc2 | |
| ...</pre> | |
| <p>then a line like</p> | |
| <pre class="screen">+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if | |
| available</pre> | |
| <p>shows that e05db0fd is reachable from itself, from v1.5.0-rc1, | |
| and from v1.5.0-rc2, and not from v1.5.0-rc0.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="showing-commits-unique-to-a-branch"></a>Showing commits unique to a given branch</h3></div></div></div> | |
| <p>Suppose you would like to see all the commits reachable from the branch | |
| head named <code class="literal">master</code> but not from any other head in your repository.</p> | |
| <p>We can list all the heads in this repository with | |
| <a class="ulink" href="git-show-ref.html" target="_top">git-show-ref(1)</a>:</p> | |
| <pre class="screen">$ git show-ref --heads | |
| bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial | |
| db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint | |
| a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master | |
| 24dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2 | |
| 1e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes</pre> | |
| <p>We can get just the branch-head names, and remove <code class="literal">master</code>, with | |
| the help of the standard utilities cut and grep:</p> | |
| <pre class="screen">$ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master' | |
| refs/heads/core-tutorial | |
| refs/heads/maint | |
| refs/heads/tutorial-2 | |
| refs/heads/tutorial-fixes</pre> | |
| <p>And then we can ask to see all the commits reachable from master | |
| but not from these other heads:</p> | |
| <pre class="screen">$ gitk master --not $( git show-ref --heads | cut -d' ' -f2 | | |
| grep -v '^refs/heads/master' )</pre> | |
| <p>Obviously, endless variations are possible; for example, to see all | |
| commits reachable from some head but not from any tag in the repository:</p> | |
| <pre class="screen">$ gitk $( git show-ref --heads ) --not $( git show-ref --tags )</pre> | |
| <p>(See <a class="ulink" href="gitrevisions.html" target="_top">gitrevisions(7)</a> for explanations of commit-selecting | |
| syntax such as <code class="literal">--not</code>.)</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="making-a-release"></a>Creating a changelog and tarball for a software release</h3></div></div></div> | |
| <p>The <a class="ulink" href="git-archive.html" target="_top">git-archive(1)</a> command can create a tar or zip archive from | |
| any version of a project; for example:</p> | |
| <pre class="screen">$ git archive -o latest.tar.gz --prefix=project/ HEAD</pre> | |
| <p>will use HEAD to produce a gzipped tar archive in which each filename | |
| is preceded by <code class="literal">project/</code>. The output file format is inferred from | |
| the output file extension if possible, see <a class="ulink" href="git-archive.html" target="_top">git-archive(1)</a> for | |
| details.</p> | |
| <p>Versions of Git older than 1.7.7 don’t know about the <code class="literal">tar.gz</code> format, | |
| you’ll need to use gzip explicitly:</p> | |
| <pre class="screen">$ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz</pre> | |
| <p>If you’re releasing a new version of a software project, you may want | |
| to simultaneously make a changelog to include in the release | |
| announcement.</p> | |
| <p>Linus Torvalds, for example, makes new kernel releases by tagging them, | |
| then running:</p> | |
| <pre class="screen">$ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7</pre> | |
| <p>where release-script is a shell script that looks like:</p> | |
| <pre class="screen">#!/bin/sh | |
| stable="$1" | |
| last="$2" | |
| new="$3" | |
| echo "# git tag v$new" | |
| echo "git archive --prefix=linux-$new/ v$new | gzip -9 > ../linux-$new.tar.gz" | |
| echo "git diff v$stable v$new | gzip -9 > ../patch-$new.gz" | |
| echo "git log --no-merges v$new ^v$last > ../ChangeLog-$new" | |
| echo "git shortlog --no-merges v$new ^v$last > ../ShortLog" | |
| echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new"</pre> | |
| <p>and then he just cut-and-pastes the output commands after verifying that | |
| they look OK.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="Finding-commits-With-given-Content"></a>Finding commits referencing a file with given content</h3></div></div></div> | |
| <p>Somebody hands you a copy of a file, and asks which commits modified a | |
| file such that it contained the given content either before or after the | |
| commit. You can find out with this:</p> | |
| <pre class="screen">$ git log --raw --abbrev=40 --pretty=oneline | | |
| grep -B 1 `git hash-object filename`</pre> | |
| <p>Figuring out why this works is left as an exercise to the (advanced) | |
| student. The <a class="ulink" href="git-log.html" target="_top">git-log(1)</a>, <a class="ulink" href="git-diff-tree.html" target="_top">git-diff-tree(1)</a>, and | |
| <a class="ulink" href="git-hash-object.html" target="_top">git-hash-object(1)</a> man pages may prove helpful.</p> | |
| </div> | |
| </div> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="Developing-With-git"></a>Chapter 3. Developing with Git</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#telling-git-your-name">Telling Git your name</a></span></dt><dt><span class="section"><a href="#creating-a-new-repository">Creating a new repository</a></span></dt><dt><span class="section"><a href="#how-to-make-a-commit">How to make a commit</a></span></dt><dt><span class="section"><a href="#creating-good-commit-messages">Creating good commit messages</a></span></dt><dt><span class="section"><a href="#ignoring-files">Ignoring files</a></span></dt><dt><span class="section"><a href="#how-to-merge">How to merge</a></span></dt><dt><span class="section"><a href="#resolving-a-merge">Resolving a merge</a></span></dt><dd><dl><dt><span class="section"><a href="#conflict-resolution">Getting conflict-resolution help during a merge</a></span></dt></dl></dd><dt><span class="section"><a href="#undoing-a-merge">Undoing a merge</a></span></dt><dt><span class="section"><a href="#fast-forwards">Fast-forward merges</a></span></dt><dt><span class="section"><a href="#fixing-mistakes">Fixing mistakes</a></span></dt><dd><dl><dt><span class="section"><a href="#reverting-a-commit">Fixing a mistake with a new commit</a></span></dt><dt><span class="section"><a href="#fixing-a-mistake-by-rewriting-history">Fixing a mistake by rewriting history</a></span></dt><dt><span class="section"><a href="#checkout-of-path">Checking out an old version of a file</a></span></dt><dt><span class="section"><a href="#interrupted-work">Temporarily setting aside work in progress</a></span></dt></dl></dd><dt><span class="section"><a href="#ensuring-good-performance">Ensuring good performance</a></span></dt><dt><span class="section"><a href="#ensuring-reliability">Ensuring reliability</a></span></dt><dd><dl><dt><span class="section"><a href="#checking-for-corruption">Checking the repository for corruption</a></span></dt><dt><span class="section"><a href="#recovering-lost-changes">Recovering lost changes</a></span></dt></dl></dd></dl></div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="telling-git-your-name"></a>Telling Git your name</h2></div></div></div> | |
| <p>Before creating any commits, you should introduce yourself to Git. | |
| The easiest way to do so is to use <a class="ulink" href="git-config.html" target="_top">git-config(1)</a>:</p> | |
| <pre class="screen">$ git config --global user.name 'Your Name Comes Here' | |
| $ git config --global user.email 'you@yourdomain.example.com'</pre> | |
| <p>Which will add the following to a file named .<code class="literal">gitconfig</code> in your | |
| home directory:</p> | |
| <pre class="screen">[user] | |
| name = Your Name Comes Here | |
| email = you@yourdomain.example.com</pre> | |
| <p>See the "CONFIGURATION FILE" section of <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for | |
| details on the configuration file. The file is plain text, so you can | |
| also edit it with your favorite editor.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="creating-a-new-repository"></a>Creating a new repository</h2></div></div></div> | |
| <p>Creating a new repository from scratch is very easy:</p> | |
| <pre class="screen">$ mkdir project | |
| $ cd project | |
| $ git init</pre> | |
| <p>If you have some initial content (say, a tarball):</p> | |
| <pre class="screen">$ tar xzvf project.tar.gz | |
| $ cd project | |
| $ git init | |
| $ git add . # include everything below ./ in the first commit: | |
| $ git commit</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-to-make-a-commit"></a>How to make a commit</h2></div></div></div> | |
| <p>Creating a new commit takes three steps:</p> | |
| <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> | |
| Making some changes to the working directory using your | |
| favorite editor. | |
| </li><li class="listitem"> | |
| Telling Git about your changes. | |
| </li><li class="listitem"> | |
| Creating the commit using the content you told Git about | |
| in step 2. | |
| </li></ol></div> | |
| <p>In practice, you can interleave and repeat steps 1 and 2 as many | |
| times as you want: in order to keep track of what you want committed | |
| at step 3, Git maintains a snapshot of the tree’s contents in a | |
| special staging area called "the index."</p> | |
| <p>At the beginning, the content of the index will be identical to | |
| that of the HEAD. The command <code class="literal">git</code> <code class="literal">diff</code> <code class="literal">--cached</code>, which shows | |
| the difference between the HEAD and the index, should therefore | |
| produce no output at that point.</p> | |
| <p>Modifying the index is easy:</p> | |
| <p>To update the index with the contents of a new or modified file, use</p> | |
| <pre class="screen">$ git add path/to/file</pre> | |
| <p>To remove a file from the index and from the working tree, use</p> | |
| <pre class="screen">$ git rm path/to/file</pre> | |
| <p>After each step you can verify that</p> | |
| <pre class="screen">$ git diff --cached</pre> | |
| <p>always shows the difference between the HEAD and the index file—this | |
| is what you’d commit if you created the commit now—and that</p> | |
| <pre class="screen">$ git diff</pre> | |
| <p>shows the difference between the working tree and the index file.</p> | |
| <p>Note that <code class="literal">git</code> <code class="literal">add</code> always adds just the current contents of a file | |
| to the index; further changes to the same file will be ignored unless | |
| you run <code class="literal">git</code> <code class="literal">add</code> on the file again.</p> | |
| <p>When you’re ready, just run</p> | |
| <pre class="screen">$ git commit</pre> | |
| <p>and Git will prompt you for a commit message and then create the new | |
| commit. Check to make sure it looks like what you expected with</p> | |
| <pre class="screen">$ git show</pre> | |
| <p>As a special shortcut,</p> | |
| <pre class="screen">$ git commit -a</pre> | |
| <p>will update the index with any files that you’ve modified or removed | |
| and create a commit, all in one step.</p> | |
| <p>A number of commands are useful for keeping track of what you’re | |
| about to commit:</p> | |
| <pre class="screen">$ git diff --cached # difference between HEAD and the index; what | |
| # would be committed if you ran "commit" now. | |
| $ git diff # difference between the index file and your | |
| # working directory; changes that would not | |
| # be included if you ran "commit" now. | |
| $ git diff HEAD # difference between HEAD and working tree; what | |
| # would be committed if you ran "commit -a" now. | |
| $ git status # a brief per-file summary of the above.</pre> | |
| <p>You can also use <a class="ulink" href="git-gui.html" target="_top">git-gui(1)</a> to create commits, view changes in | |
| the index and the working tree files, and individually select diff hunks | |
| for inclusion in the index (by right-clicking on the diff hunk and | |
| choosing "Stage Hunk For Commit").</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="creating-good-commit-messages"></a>Creating good commit messages</h2></div></div></div> | |
| <p>Though not required, it’s a good idea to begin the commit message | |
| with a single short (no more than 50 characters) line summarizing the | |
| change, followed by a blank line and then a more thorough | |
| description. The text up to the first blank line in a commit | |
| message is treated as the commit title, and that title is used | |
| throughout Git. For example, <a class="ulink" href="git-format-patch.html" target="_top">git-format-patch(1)</a> turns a | |
| commit into email, and it uses the title on the Subject line and the | |
| rest of the commit in the body.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ignoring-files"></a>Ignoring files</h2></div></div></div> | |
| <p>A project will often generate files that you do <span class="emphasis"><em>not</em></span> want to track with Git. | |
| This typically includes files generated by a build process or temporary | |
| backup files made by your editor. Of course, <span class="emphasis"><em>not</em></span> tracking files with Git | |
| is just a matter of <span class="emphasis"><em>not</em></span> calling <code class="literal">git</code> <code class="literal">add</code> on them. But it quickly becomes | |
| annoying to have these untracked files lying around; e.g. they make | |
| <code class="literal">git</code> <code class="literal">add</code> . practically useless, and they keep showing up in the output of | |
| <code class="literal">git</code> <code class="literal">status</code>.</p> | |
| <p>You can tell Git to ignore certain files by creating a file called | |
| .<code class="literal">gitignore</code> in the top level of your working directory, with contents | |
| such as:</p> | |
| <pre class="screen"># Lines starting with '#' are considered comments. | |
| # Ignore any file named foo.txt. | |
| foo.txt | |
| # Ignore (generated) html files, | |
| *.html | |
| # except foo.html which is maintained by hand. | |
| !foo.html | |
| # Ignore objects and archives. | |
| *.[oa]</pre> | |
| <p>See <a class="ulink" href="gitignore.html" target="_top">gitignore(5)</a> for a detailed explanation of the syntax. You can | |
| also place .gitignore files in other directories in your working tree, and they | |
| will apply to those directories and their subdirectories. The .<code class="literal">gitignore</code> | |
| files can be added to your repository like any other files (just run <code class="literal">git</code> <code class="literal">add</code> | |
| <code class="literal">.gitignore</code> and <code class="literal">git</code> <code class="literal">commit</code>, as usual), which is convenient when the exclude | |
| patterns (such as patterns matching build output files) would also make sense | |
| for other users who clone your repository.</p> | |
| <p>If you wish the exclude patterns to affect only certain repositories | |
| (instead of every repository for a given project), you may instead put | |
| them in a file in your repository named .<code class="literal">git/info/exclude</code>, or in any | |
| file specified by the <code class="literal">core.excludesFile</code> configuration variable. | |
| Some Git commands can also take exclude patterns directly on the | |
| command line. See <a class="ulink" href="gitignore.html" target="_top">gitignore(5)</a> for the details.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-to-merge"></a>How to merge</h2></div></div></div> | |
| <p>You can rejoin two diverging branches of development using | |
| <a class="ulink" href="git-merge.html" target="_top">git-merge(1)</a>:</p> | |
| <pre class="screen">$ git merge branchname</pre> | |
| <p>merges the development in the branch <code class="literal">branchname</code> into the current | |
| branch.</p> | |
| <p>A merge is made by combining the changes made in <code class="literal">branchname</code> and the | |
| changes made up to the latest commit in your current branch since | |
| their histories forked. The work tree is overwritten by the result of | |
| the merge when this combining is done cleanly, or overwritten by a | |
| half-merged results when this combining results in conflicts. | |
| Therefore, if you have uncommitted changes touching the same files as | |
| the ones impacted by the merge, Git will refuse to proceed. Most of | |
| the time, you will want to commit your changes before you can merge, | |
| and if you don’t, then <a class="ulink" href="git-stash.html" target="_top">git-stash(1)</a> can take these changes | |
| away while you’re doing the merge, and reapply them afterwards.</p> | |
| <p>If the changes are independent enough, Git will automatically complete | |
| the merge and commit the result (or reuse an existing commit in case | |
| of <a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a>, see below). On the other hand, | |
| if there are conflicts—for example, if the same file is | |
| modified in two different ways in the remote branch and the local | |
| branch—then you are warned; the output may look something like this:</p> | |
| <pre class="screen">$ git merge next | |
| 100% (4/4) done | |
| Auto-merged file.txt | |
| CONFLICT (content): Merge conflict in file.txt | |
| Automatic merge failed; fix conflicts and then commit the result.</pre> | |
| <p>Conflict markers are left in the problematic files, and after | |
| you resolve the conflicts manually, you can update the index | |
| with the contents and run Git commit, as you normally would when | |
| creating a new file.</p> | |
| <p>If you examine the resulting commit using gitk, you will see that it | |
| has two parents, one pointing to the top of the current branch, and | |
| one to the top of the other branch.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="resolving-a-merge"></a>Resolving a merge</h2></div></div></div> | |
| <p>When a merge isn’t resolved automatically, Git leaves the index and | |
| the working tree in a special state that gives you all the | |
| information you need to help resolve the merge.</p> | |
| <p>Files with conflicts are marked specially in the index, so until you | |
| resolve the problem and update the index, <a class="ulink" href="git-commit.html" target="_top">git-commit(1)</a> will | |
| fail:</p> | |
| <pre class="screen">$ git commit | |
| file.txt: needs merge</pre> | |
| <p>Also, <a class="ulink" href="git-status.html" target="_top">git-status(1)</a> will list those files as "unmerged", and the | |
| files with conflicts will have conflict markers added, like this:</p> | |
| <pre class="screen"><<<<<<< HEAD:file.txt | |
| Hello world | |
| ======= | |
| Goodbye | |
| >>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt</pre> | |
| <p>All you need to do is edit the files to resolve the conflicts, and then</p> | |
| <pre class="screen">$ git add file.txt | |
| $ git commit</pre> | |
| <p>Note that the commit message will already be filled in for you with | |
| some information about the merge. Normally you can just use this | |
| default message unchanged, but you may add additional commentary of | |
| your own if desired.</p> | |
| <p>The above is all you need to know to resolve a simple merge. But Git | |
| also provides more information to help resolve conflicts:</p> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="conflict-resolution"></a>Getting conflict-resolution help during a merge</h3></div></div></div> | |
| <p>All of the changes that Git was able to merge automatically are | |
| already added to the index file, so <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a> shows only | |
| the conflicts. It uses an unusual syntax:</p> | |
| <pre class="screen">$ git diff | |
| diff --cc file.txt | |
| index 802992c,2b60207..0000000 | |
| --- a/file.txt | |
| +++ b/file.txt | |
| @@@ -1,1 -1,1 +1,5 @@@ | |
| ++<<<<<<< HEAD:file.txt | |
| +Hello world | |
| ++======= | |
| + Goodbye | |
| ++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt</pre> | |
| <p>Recall that the commit which will be committed after we resolve this | |
| conflict will have two parents instead of the usual one: one parent | |
| will be HEAD, the tip of the current branch; the other will be the | |
| tip of the other branch, which is stored temporarily in MERGE_HEAD.</p> | |
| <p>During the merge, the index holds three versions of each file. Each of | |
| these three "file stages" represents a different version of the file:</p> | |
| <pre class="screen">$ git show :1:file.txt # the file in a common ancestor of both branches | |
| $ git show :2:file.txt # the version from HEAD. | |
| $ git show :3:file.txt # the version from MERGE_HEAD.</pre> | |
| <p>When you ask <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a> to show the conflicts, it runs a | |
| three-way diff between the conflicted merge results in the work tree with | |
| stages 2 and 3 to show only hunks whose contents come from both sides, | |
| mixed (in other words, when a hunk’s merge results come only from stage 2, | |
| that part is not conflicting and is not shown. Same for stage 3).</p> | |
| <p>The diff above shows the differences between the working-tree version of | |
| file.txt and the stage 2 and stage 3 versions. So instead of preceding | |
| each line by a single <code class="literal">+</code> or <code class="literal">-</code>, it now uses two columns: the first | |
| column is used for differences between the first parent and the working | |
| directory copy, and the second for differences between the second parent | |
| and the working directory copy. (See the "COMBINED DIFF FORMAT" section | |
| of <a class="ulink" href="git-diff-files.html" target="_top">git-diff-files(1)</a> for a details of the format.)</p> | |
| <p>After resolving the conflict in the obvious way (but before updating the | |
| index), the diff will look like:</p> | |
| <pre class="screen">$ git diff | |
| diff --cc file.txt | |
| index 802992c,2b60207..0000000 | |
| --- a/file.txt | |
| +++ b/file.txt | |
| @@@ -1,1 -1,1 +1,1 @@@ | |
| - Hello world | |
| -Goodbye | |
| ++Goodbye world</pre> | |
| <p>This shows that our resolved version deleted "Hello world" from the | |
| first parent, deleted "Goodbye" from the second parent, and added | |
| "Goodbye world", which was previously absent from both.</p> | |
| <p>Some special diff options allow diffing the working directory against | |
| any of these stages:</p> | |
| <pre class="screen">$ git diff -1 file.txt # diff against stage 1 | |
| $ git diff --base file.txt # same as the above | |
| $ git diff -2 file.txt # diff against stage 2 | |
| $ git diff --ours file.txt # same as the above | |
| $ git diff -3 file.txt # diff against stage 3 | |
| $ git diff --theirs file.txt # same as the above.</pre> | |
| <p>When using the <span class="emphasis"><em>ort</em></span> merge strategy (the default), before updating the working | |
| tree with the result of the merge, Git writes a ref named AUTO_MERGE | |
| reflecting the state of the tree it is about to write. Conflicted paths with | |
| textual conflicts that could not be automatically merged are written to this | |
| tree with conflict markers, just as in the working tree. AUTO_MERGE can thus be | |
| used with <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a> to show the changes you’ve made so far to resolve | |
| conflicts. Using the same example as above, after resolving the conflict we | |
| get:</p> | |
| <pre class="screen">$ git diff AUTO_MERGE | |
| diff --git a/file.txt b/file.txt | |
| index cd10406..8bf5ae7 100644 | |
| --- a/file.txt | |
| +++ b/file.txt | |
| @@ -1,5 +1 @@ | |
| -<<<<<<< HEAD:file.txt | |
| -Hello world | |
| -======= | |
| -Goodbye | |
| ->>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt | |
| +Goodbye world</pre> | |
| <p>Notice that the diff shows we deleted the conflict markers and both versions of | |
| the content line, and wrote "Goodbye world" instead.</p> | |
| <p>The <a class="ulink" href="git-log.html" target="_top">git-log(1)</a> and <a class="ulink" href="gitk.html" target="_top">gitk(1)</a> commands also provide special help | |
| for merges:</p> | |
| <pre class="screen">$ git log --merge | |
| $ gitk --merge</pre> | |
| <p>These will display all commits which exist only on HEAD or on | |
| MERGE_HEAD, and which touch an unmerged file.</p> | |
| <p>You may also use <a class="ulink" href="git-mergetool.html" target="_top">git-mergetool(1)</a>, which lets you merge the | |
| unmerged files using external tools such as Emacs or kdiff3.</p> | |
| <p>Each time you resolve the conflicts in a file and update the index:</p> | |
| <pre class="screen">$ git add file.txt</pre> | |
| <p>the different stages of that file will be "collapsed", after which | |
| <code class="literal">git</code> <code class="literal">diff</code> will (by default) no longer show diffs for that file.</p> | |
| </div> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="undoing-a-merge"></a>Undoing a merge</h2></div></div></div> | |
| <p>If you get stuck and decide to just give up and throw the whole mess | |
| away, you can always return to the pre-merge state with</p> | |
| <pre class="screen">$ git merge --abort</pre> | |
| <p>Or, if you’ve already committed the merge that you want to throw away,</p> | |
| <pre class="screen">$ git reset --hard ORIG_HEAD</pre> | |
| <p>However, this last command can be dangerous in some cases—never | |
| throw away a commit you have already committed if that commit may | |
| itself have been merged into another branch, as doing so may confuse | |
| further merges.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fast-forwards"></a>Fast-forward merges</h2></div></div></div> | |
| <p>There is one special case not mentioned above, which is treated | |
| differently. Normally, a merge results in a merge commit, with two | |
| parents, one pointing at each of the two lines of development that | |
| were merged.</p> | |
| <p>However, if the current branch is an ancestor of the other—so every commit | |
| present in the current branch is already contained in the other branch—then Git | |
| just performs a "fast-forward"; the head of the current branch is moved forward | |
| to point at the head of the merged-in branch, without any new commits being | |
| created.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fixing-mistakes"></a>Fixing mistakes</h2></div></div></div> | |
| <p>If you’ve messed up the working tree, but haven’t yet committed your | |
| mistake, you can return the entire working tree to the last committed | |
| state with</p> | |
| <pre class="screen">$ git restore --staged --worktree :/</pre> | |
| <p>If you make a commit that you later wish you hadn’t, there are two | |
| fundamentally different ways to fix the problem:</p> | |
| <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> | |
| You can create a new commit that undoes whatever was done | |
| by the old commit. This is the correct thing if your | |
| mistake has already been made public. | |
| </li><li class="listitem"> | |
| You can go back and modify the old commit. You should | |
| never do this if you have already made the history public; | |
| Git does not normally expect the "history" of a project to | |
| change, and cannot correctly perform repeated merges from | |
| a branch that has had its history changed. | |
| </li></ol></div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="reverting-a-commit"></a>Fixing a mistake with a new commit</h3></div></div></div> | |
| <p>Creating a new commit that reverts an earlier change is very easy; | |
| just pass the <a class="ulink" href="git-revert.html" target="_top">git-revert(1)</a> command a reference to the bad | |
| commit; for example, to revert the most recent commit:</p> | |
| <pre class="screen">$ git revert HEAD</pre> | |
| <p>This will create a new commit which undoes the change in HEAD. You | |
| will be given a chance to edit the commit message for the new commit.</p> | |
| <p>You can also revert an earlier change, for example, the next-to-last:</p> | |
| <pre class="screen">$ git revert HEAD^</pre> | |
| <p>In this case Git will attempt to undo the old change while leaving | |
| intact any changes made since then. If more recent changes overlap | |
| with the changes to be reverted, then you will be asked to fix | |
| conflicts manually, just as in the case of <a class="link" href="#resolving-a-merge" title="Resolving a merge">resolving a merge</a>.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="fixing-a-mistake-by-rewriting-history"></a>Fixing a mistake by rewriting history</h3></div></div></div> | |
| <p>If the problematic commit is the most recent commit, and you have not | |
| yet made that commit public, then you may just | |
| <a class="link" href="#undoing-a-merge" title="Undoing a merge">destroy it using <code class="literal">git</code> <code class="literal">reset</code></a>.</p> | |
| <p>Alternatively, you | |
| can edit the working directory and update the index to fix your | |
| mistake, just as if you were going to <a class="link" href="#how-to-make-a-commit" title="How to make a commit">create a | |
| new commit</a>, then run</p> | |
| <pre class="screen">$ git commit --amend</pre> | |
| <p>which will replace the old commit by a new commit incorporating your | |
| changes, giving you a chance to edit the old commit message first.</p> | |
| <p>Again, you should never do this to a commit that may already have | |
| been merged into another branch; use <a class="ulink" href="git-revert.html" target="_top">git-revert(1)</a> instead in | |
| that case.</p> | |
| <p>It is also possible to replace commits further back in the history, but | |
| this is an advanced topic to be left for | |
| <a class="link" href="#cleaning-up-history" title="Chapter 5. Rewriting history and maintaining patch series">another chapter</a>.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="checkout-of-path"></a>Checking out an old version of a file</h3></div></div></div> | |
| <p>In the process of undoing a previous bad change, you may find it | |
| useful to check out an older version of a particular file using | |
| <a class="ulink" href="git-restore.html" target="_top">git-restore(1)</a>. The command</p> | |
| <pre class="screen">$ git restore --source=HEAD^ path/to/file</pre> | |
| <p>replaces path/to/file by the contents it had in the commit HEAD^, and | |
| also updates the index to match. It does not change branches.</p> | |
| <p>If you just want to look at an old version of the file, without | |
| modifying the working directory, you can do that with | |
| <a class="ulink" href="git-show.html" target="_top">git-show(1)</a>:</p> | |
| <pre class="screen">$ git show HEAD^:path/to/file</pre> | |
| <p>which will display the given version of the file.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="interrupted-work"></a>Temporarily setting aside work in progress</h3></div></div></div> | |
| <p>While you are in the middle of working on something complicated, you | |
| find an unrelated but obvious and trivial bug. You would like to fix it | |
| before continuing. You can use <a class="ulink" href="git-stash.html" target="_top">git-stash(1)</a> to save the current | |
| state of your work, and after fixing the bug (or, optionally after doing | |
| so on a different branch and then coming back), unstash the | |
| work-in-progress changes.</p> | |
| <pre class="screen">$ git stash push -m "work in progress for foo feature"</pre> | |
| <p>This command will save your changes away to the <code class="literal">stash</code>, and | |
| reset your working tree and the index to match the tip of your | |
| current branch. Then you can make your fix as usual.</p> | |
| <pre class="screen">... edit and test ... | |
| $ git commit -a -m "blorpl: typofix"</pre> | |
| <p>After that, you can go back to what you were working on with | |
| <code class="literal">git</code> <code class="literal">stash</code> <code class="literal">pop</code>:</p> | |
| <pre class="screen">$ git stash pop</pre> | |
| </div> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ensuring-good-performance"></a>Ensuring good performance</h2></div></div></div> | |
| <p>On large repositories, Git depends on compression to keep the history | |
| information from taking up too much space on disk or in memory. Some | |
| Git commands may automatically run <a class="ulink" href="git-gc.html" target="_top">git-gc(1)</a>, so you don’t | |
| have to worry about running it manually. However, compressing a large | |
| repository may take a while, so you may want to call <code class="literal">gc</code> explicitly | |
| to avoid automatic compression kicking in when it is not convenient.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ensuring-reliability"></a>Ensuring reliability</h2></div></div></div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="checking-for-corruption"></a>Checking the repository for corruption</h3></div></div></div> | |
| <p>The <a class="ulink" href="git-fsck.html" target="_top">git-fsck(1)</a> command runs a number of self-consistency checks | |
| on the repository, and reports on any problems. This may take some | |
| time.</p> | |
| <pre class="screen">$ git fsck | |
| dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 | |
| dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 | |
| dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 | |
| dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb | |
| dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f | |
| dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e | |
| dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085 | |
| dangling tree b24c2473f1fd3d91352a624795be026d64c8841f | |
| ...</pre> | |
| <p>You will see informational messages on dangling objects. They are objects | |
| that still exist in the repository but are no longer referenced by any of | |
| your branches, and can (and will) be removed after a while with <code class="literal">gc</code>. | |
| You can run <code class="literal">git</code> <code class="literal">fsck</code> <code class="literal">--no-dangling</code> to suppress these messages, and still | |
| view real errors.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="recovering-lost-changes"></a>Recovering lost changes</h3></div></div></div> | |
| <div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="reflogs"></a>Reflogs</h4></div></div></div> | |
| <p>Say you modify a branch with <a class="link" href="#fixing-mistakes" title="Fixing mistakes"><code class="literal">git</code> <code class="literal">reset</code> <code class="literal">--hard</code></a>, | |
| and then realize that the branch was the only reference you had to | |
| that point in history.</p> | |
| <p>Fortunately, Git also keeps a log, called a "reflog", of all the | |
| previous values of each branch. So in this case you can still find the | |
| old history using, for example,</p> | |
| <pre class="screen">$ git log master@{1}</pre> | |
| <p>This lists the commits reachable from the previous version of the | |
| <code class="literal">master</code> branch head. This syntax can be used with any Git command | |
| that accepts a commit, not just with <code class="literal">git</code> <code class="literal">log</code>. Some other examples:</p> | |
| <pre class="screen">$ git show master@{2} # See where the branch pointed 2, | |
| $ git show master@{3} # 3, ... changes ago. | |
| $ gitk master@{yesterday} # See where it pointed yesterday, | |
| $ gitk master@{"1 week ago"} # ... or last week | |
| $ git log --walk-reflogs master # show reflog entries for master</pre> | |
| <p>A separate reflog is kept for the HEAD, so</p> | |
| <pre class="screen">$ git show HEAD@{"1 week ago"}</pre> | |
| <p>will show what HEAD pointed to one week ago, not what the current branch | |
| pointed to one week ago. This allows you to see the history of what | |
| you’ve checked out.</p> | |
| <p>The reflogs are kept by default for 30 days, after which they may be | |
| pruned. See <a class="ulink" href="git-reflog.html" target="_top">git-reflog(1)</a> and <a class="ulink" href="git-gc.html" target="_top">git-gc(1)</a> to learn | |
| how to control this pruning, and see the "SPECIFYING REVISIONS" | |
| section of <a class="ulink" href="gitrevisions.html" target="_top">gitrevisions(7)</a> for details.</p> | |
| <p>Note that the reflog history is very different from normal Git history. | |
| While normal history is shared by every repository that works on the | |
| same project, the reflog history is not shared: it tells you only about | |
| how the branches in your local repository have changed over time.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="dangling-object-recovery"></a>Examining dangling objects</h4></div></div></div> | |
| <p>In some situations the reflog may not be able to save you. For example, | |
| suppose you delete a branch, then realize you need the history it | |
| contained. The reflog is also deleted; however, if you have not yet | |
| pruned the repository, then you may still be able to find the lost | |
| commits in the dangling objects that <code class="literal">git</code> <code class="literal">fsck</code> reports. See | |
| <a class="xref" href="#dangling-objects" title="Dangling objects">the section called “Dangling objects”</a> for the details.</p> | |
| <pre class="screen">$ git fsck | |
| dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 | |
| dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 | |
| dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 | |
| ...</pre> | |
| <p>You can examine | |
| one of those dangling commits with, for example,</p> | |
| <pre class="screen">$ gitk 7281251ddd --not --all</pre> | |
| <p>which does what it sounds like: it says that you want to see the commit | |
| history that is described by the dangling commit(s), but not the | |
| history that is described by all your existing branches and tags. Thus | |
| you get exactly the history reachable from that commit that is lost. | |
| (And notice that it might not be just one commit: we only report the | |
| "tip of the line" as being dangling, but there might be a whole deep | |
| and complex commit history that was dropped.)</p> | |
| <p>If you decide you want the history back, you can always create a new | |
| reference pointing to it, for example, a new branch:</p> | |
| <pre class="screen">$ git branch recovered-branch 7281251ddd</pre> | |
| <p>Other types of dangling objects (blobs and trees) are also possible, and | |
| dangling objects can arise in other situations.</p> | |
| </div> | |
| </div> | |
| </div> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="sharing-development"></a>Chapter 4. Sharing development with others</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#getting-updates-With-git-pull">Getting updates with git pull</a></span></dt><dt><span class="section"><a href="#submitting-patches">Submitting patches to a project</a></span></dt><dt><span class="section"><a href="#importing-patches">Importing patches to a project</a></span></dt><dt><span class="section"><a href="#public-repositories">Public Git repositories</a></span></dt><dd><dl><dt><span class="section"><a href="#setting-up-a-public-repository">Setting up a public repository</a></span></dt><dt><span class="section"><a href="#exporting-via-git">Exporting a Git repository via the Git protocol</a></span></dt><dt><span class="section"><a href="#exporting-via-http">Exporting a git repository via HTTP</a></span></dt><dt><span class="section"><a href="#pushing-changes-to-a-public-repository">Pushing changes to a public repository</a></span></dt><dt><span class="section"><a href="#forcing-push">What to do when a push fails</a></span></dt><dt><span class="section"><a href="#setting-up-a-shared-repository">Setting up a shared repository</a></span></dt><dt><span class="section"><a href="#setting-up-gitweb">Allowing web browsing of a repository</a></span></dt></dl></dd><dt><span class="section"><a href="#how-to-get-a-git-repository-with-minimal-history">How to get a Git repository with minimal history</a></span></dt><dt><span class="section"><a href="#sharing-development-examples">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#maintaining-topic-branches">Maintaining topic branches for a Linux subsystem maintainer</a></span></dt></dl></dd></dl></div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="getting-updates-With-git-pull"></a>Getting updates with git pull</h2></div></div></div> | |
| <p>After you clone a repository and commit a few changes of your own, you | |
| may wish to check the original repository for updates and merge them | |
| into your own work.</p> | |
| <p>We have already seen <a class="link" href="#Updating-a-repository-With-git-fetch" title="Updating a repository with git fetch">how to | |
| keep remote-tracking branches up to date</a> with <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a>, | |
| and how to merge two branches. So you can merge in changes from the | |
| original repository’s master branch with:</p> | |
| <pre class="screen">$ git fetch | |
| $ git merge origin/master</pre> | |
| <p>However, the <a class="ulink" href="git-pull.html" target="_top">git-pull(1)</a> command provides a way to do this in | |
| one step:</p> | |
| <pre class="screen">$ git pull origin master</pre> | |
| <p>In fact, if you have <code class="literal">master</code> checked out, then this branch has been | |
| configured by <code class="literal">git</code> <code class="literal">clone</code> to get changes from the HEAD branch of the | |
| origin repository. So often you can | |
| accomplish the above with just a simple</p> | |
| <pre class="screen">$ git pull</pre> | |
| <p>This command will fetch changes from the remote branches to your | |
| remote-tracking branches <code class="literal">origin/*</code>, and merge the default branch into | |
| the current branch.</p> | |
| <p>More generally, a branch that is created from a remote-tracking branch | |
| will pull | |
| by default from that branch. See the descriptions of the | |
| <code class="literal">branch.</code><span class="emphasis"><em><name></em></span><code class="literal">.remote</code> and <code class="literal">branch.</code><span class="emphasis"><em><name></em></span><code class="literal">.merge</code> options in | |
| <a class="ulink" href="git-config.html" target="_top">git-config(1)</a>, and the discussion of the <code class="literal">--track</code> option in | |
| <a class="ulink" href="git-checkout.html" target="_top">git-checkout(1)</a>, to learn how to control these defaults.</p> | |
| <p>In addition to saving you keystrokes, <code class="literal">git</code> <code class="literal">pull</code> also helps you by | |
| producing a default commit message documenting the branch and | |
| repository that you pulled from.</p> | |
| <p>(But note that no such commit will be created in the case of a | |
| <a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a>; instead, your branch will just be | |
| updated to point to the latest commit from the upstream branch.)</p> | |
| <p>The <code class="literal">git</code> <code class="literal">pull</code> command can also be given . as the "remote" repository, | |
| in which case it just merges in a branch from the current repository; so | |
| the commands</p> | |
| <pre class="screen">$ git pull . branch | |
| $ git merge branch</pre> | |
| <p>are roughly equivalent.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="submitting-patches"></a>Submitting patches to a project</h2></div></div></div> | |
| <p>If you just have a few changes, the simplest way to submit them may | |
| just be to send them as patches in email:</p> | |
| <p>First, use <a class="ulink" href="git-format-patch.html" target="_top">git-format-patch(1)</a>; for example:</p> | |
| <pre class="screen">$ git format-patch origin</pre> | |
| <p>will produce a numbered series of files in the current directory, one | |
| for each patch in the current branch but not in <code class="literal">origin/HEAD</code>.</p> | |
| <p><code class="literal">git</code> <code class="literal">format-patch</code> can include an initial "cover letter". You can insert | |
| commentary on individual patches after the three dash line which | |
| <code class="literal">format-patch</code> places after the commit message but before the patch | |
| itself. If you use <code class="literal">git</code> <code class="literal">notes</code> to track your cover letter material, | |
| <code class="literal">git</code> <code class="literal">format-patch</code> <code class="literal">--notes</code> will include the commit’s notes in a similar | |
| manner.</p> | |
| <p>You can then import these into your mail client and send them by | |
| hand. However, if you have a lot to send at once, you may prefer to | |
| use the <a class="ulink" href="git-send-email.html" target="_top">git-send-email(1)</a> script to automate the process. | |
| Consult the mailing list for your project first to determine | |
| their requirements for submitting patches.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="importing-patches"></a>Importing patches to a project</h2></div></div></div> | |
| <p>Git also provides a tool called <a class="ulink" href="git-am.html" target="_top">git-am(1)</a> (am stands for | |
| "apply mailbox"), for importing such an emailed series of patches. | |
| Just save all of the patch-containing messages, in order, into a | |
| single mailbox file, say <code class="literal">patches.mbox</code>, then run</p> | |
| <pre class="screen">$ git am -3 patches.mbox</pre> | |
| <p>Git will apply each patch in order; if any conflicts are found, it | |
| will stop, and you can fix the conflicts as described in | |
| "<a class="link" href="#resolving-a-merge" title="Resolving a merge">Resolving a merge</a>". (The <code class="literal">-3</code> option tells | |
| Git to perform a merge; if you would prefer it just to abort and | |
| leave your tree and index untouched, you may omit that option.)</p> | |
| <p>Once the index is updated with the results of the conflict | |
| resolution, instead of creating a new commit, just run</p> | |
| <pre class="screen">$ git am --continue</pre> | |
| <p>and Git will create the commit for you and continue applying the | |
| remaining patches from the mailbox.</p> | |
| <p>The final result will be a series of commits, one for each patch in | |
| the original mailbox, with authorship and commit log message each | |
| taken from the message containing each patch.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="public-repositories"></a>Public Git repositories</h2></div></div></div> | |
| <p>Another way to submit changes to a project is to tell the maintainer | |
| of that project to pull the changes from your repository using | |
| <a class="ulink" href="git-pull.html" target="_top">git-pull(1)</a>. In the section "<a class="link" href="#getting-updates-With-git-pull" title="Getting updates with git pull">Getting updates with <code class="literal">git</code> <code class="literal">pull</code></a>" we described this as a way to get | |
| updates from the "main" repository, but it works just as well in the | |
| other direction.</p> | |
| <p>If you and the maintainer both have accounts on the same machine, then | |
| you can just pull changes from each other’s repositories directly; | |
| commands that accept repository URLs as arguments will also accept a | |
| local directory name:</p> | |
| <pre class="screen">$ git clone /path/to/repository | |
| $ git pull /path/to/other/repository</pre> | |
| <p>or an ssh URL:</p> | |
| <pre class="screen">$ git clone ssh://yourhost/~you/repository</pre> | |
| <p>For projects with few developers, or for synchronizing a few private | |
| repositories, this may be all you need.</p> | |
| <p>However, the more common way to do this is to maintain a separate public | |
| repository (usually on a different host) for others to pull changes | |
| from. This is usually more convenient, and allows you to cleanly | |
| separate private work in progress from publicly visible work.</p> | |
| <p>You will continue to do your day-to-day work in your personal | |
| repository, but periodically "push" changes from your personal | |
| repository into your public repository, allowing other developers to | |
| pull from that repository. So the flow of changes, in a situation | |
| where there is one other developer with a public repository, looks | |
| like this:</p> | |
| <pre class="literallayout"> you push | |
| your personal repo ------------------> your public repo | |
| ^ | | |
| | | | |
| | you pull | they pull | |
| | | | |
| | | | |
| | they push V | |
| their public repo <------------------- their repo</pre> | |
| <p>We explain how to do this in the following sections.</p> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="setting-up-a-public-repository"></a>Setting up a public repository</h3></div></div></div> | |
| <p>Assume your personal repository is in the directory <code class="literal">~/proj</code>. We | |
| first create a new clone of the repository and tell <code class="literal">git</code> <code class="literal">daemon</code> that it | |
| is meant to be public:</p> | |
| <pre class="screen">$ git clone --bare ~/proj proj.git | |
| $ touch proj.git/git-daemon-export-ok</pre> | |
| <p>The resulting directory proj.git contains a "bare" git repository—it is | |
| just the contents of the .<code class="literal">git</code> directory, without any files checked out | |
| around it.</p> | |
| <p>Next, copy <code class="literal">proj.git</code> to the server where you plan to host the | |
| public repository. You can use scp, rsync, or whatever is most | |
| convenient.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="exporting-via-git"></a>Exporting a Git repository via the Git protocol</h3></div></div></div> | |
| <p>This is the preferred method.</p> | |
| <p>If someone else administers the server, they should tell you what | |
| directory to put the repository in, and what <code class="literal">git://</code> URL it will | |
| appear at. You can then skip to the section | |
| "<a class="link" href="#pushing-changes-to-a-public-repository" title="Pushing changes to a public repository">Pushing changes to a public | |
| repository</a>", below.</p> | |
| <p>Otherwise, all you need to do is start <a class="ulink" href="git-daemon.html" target="_top">git-daemon(1)</a>; it will | |
| listen on port 9418. By default, it will allow access to any directory | |
| that looks like a Git directory and contains the magic file | |
| git-daemon-export-ok. Passing some directory paths as <code class="literal">git</code> <code class="literal">daemon</code> | |
| arguments will further restrict the exports to those paths.</p> | |
| <p>You can also run <code class="literal">git</code> <code class="literal">daemon</code> as an inetd service; see the | |
| <a class="ulink" href="git-daemon.html" target="_top">git-daemon(1)</a> man page for details. (See especially the | |
| examples section.)</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="exporting-via-http"></a>Exporting a git repository via HTTP</h3></div></div></div> | |
| <p>The Git protocol gives better performance and reliability, but on a | |
| host with a web server set up, HTTP exports may be simpler to set up.</p> | |
| <p>All you need to do is place the newly created bare Git repository in | |
| a directory that is exported by the web server, and make some | |
| adjustments to give web clients some extra information they need:</p> | |
| <pre class="screen">$ mv proj.git /home/you/public_html/proj.git | |
| $ cd proj.git | |
| $ git --bare update-server-info | |
| $ mv hooks/post-update.sample hooks/post-update</pre> | |
| <p>(For an explanation of the last two lines, see | |
| <a class="ulink" href="git-update-server-info.html" target="_top">git-update-server-info(1)</a> and <a class="ulink" href="githooks.html" target="_top">githooks(5)</a>.)</p> | |
| <p>Advertise the URL of <code class="literal">proj.git</code>. Anybody else should then be able to | |
| clone or pull from that URL, for example with a command line like:</p> | |
| <pre class="screen">$ git clone http://yourserver.com/~you/proj.git</pre> | |
| <p>(See also | |
| <a class="ulink" href="howto/setup-git-server-over-http.html" target="_top">setup-git-server-over-http</a> | |
| for a slightly more sophisticated setup using WebDAV which also | |
| allows pushing over HTTP.)</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="pushing-changes-to-a-public-repository"></a>Pushing changes to a public repository</h3></div></div></div> | |
| <p>Note that the two techniques outlined above (exporting via | |
| <a class="link" href="#exporting-via-http" title="Exporting a git repository via HTTP">http</a> or <a class="link" href="#exporting-via-git" title="Exporting a Git repository via the Git protocol">git</a>) allow other | |
| maintainers to fetch your latest changes, but they do not allow write | |
| access, which you will need to update the public repository with the | |
| latest changes created in your private repository.</p> | |
| <p>The simplest way to do this is using <a class="ulink" href="git-push.html" target="_top">git-push(1)</a> and ssh; to | |
| update the remote branch named <code class="literal">master</code> with the latest state of your | |
| branch named <code class="literal">master</code>, run</p> | |
| <pre class="screen">$ git push ssh://yourserver.com/~you/proj.git master:master</pre> | |
| <p>or just</p> | |
| <pre class="screen">$ git push ssh://yourserver.com/~you/proj.git master</pre> | |
| <p>As with <code class="literal">git</code> <code class="literal">fetch</code>, <code class="literal">git</code> <code class="literal">push</code> will complain if this does not result in a | |
| <a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a>; see the following section for details on | |
| handling this case.</p> | |
| <p>Note that the target of a <code class="literal">push</code> is normally a | |
| <a class="link" href="#def_bare_repository">bare</a> repository. You can also push to a | |
| repository that has a checked-out working tree, but a push to update the | |
| currently checked-out branch is denied by default to prevent confusion. | |
| See the description of the receive.denyCurrentBranch option | |
| in <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for details.</p> | |
| <p>As with <code class="literal">git</code> <code class="literal">fetch</code>, you may also set up configuration options to | |
| save typing; so, for example:</p> | |
| <pre class="screen">$ git remote add public-repo ssh://yourserver.com/~you/proj.git</pre> | |
| <p>adds the following to .<code class="literal">git/config</code>:</p> | |
| <pre class="screen">[remote "public-repo"] | |
| url = yourserver.com:proj.git | |
| fetch = +refs/heads/*:refs/remotes/example/*</pre> | |
| <p>which lets you do the same push with just</p> | |
| <pre class="screen">$ git push public-repo master</pre> | |
| <p>See the explanations of the <code class="literal">remote.</code><span class="emphasis"><em><name></em></span><code class="literal">.url</code>, | |
| <code class="literal">branch.</code><span class="emphasis"><em><name></em></span><code class="literal">.remote</code>, and <code class="literal">remote.</code><span class="emphasis"><em><name></em></span><code class="literal">.push</code> options in | |
| <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for details.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="forcing-push"></a>What to do when a push fails</h3></div></div></div> | |
| <p>If a push would not result in a <a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a> of the | |
| remote branch, then it will fail with an error like:</p> | |
| <pre class="screen"> ! [rejected] master -> master (non-fast-forward) | |
| error: failed to push some refs to '...' | |
| hint: Updates were rejected because the tip of your current branch is behind | |
| hint: its remote counterpart. Integrate the remote changes (e.g. | |
| hint: 'git pull ...') before pushing again. | |
| hint: See the 'Note about fast-forwards' in 'git push --help' for details.</pre> | |
| <p>This can happen, for example, if you:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| use <code class="literal">git</code> <code class="literal">reset</code> <code class="literal">--hard</code> to remove already-published commits, or | |
| </li><li class="listitem"> | |
| use <code class="literal">git</code> <code class="literal">commit</code> <code class="literal">--amend</code> to replace already-published commits | |
| (as in <a class="xref" href="#fixing-a-mistake-by-rewriting-history" title="Fixing a mistake by rewriting history">the section called “Fixing a mistake by rewriting history”</a>), or | |
| </li><li class="listitem"> | |
| use <code class="literal">git</code> <code class="literal">rebase</code> to rebase any already-published commits (as | |
| in <a class="xref" href="#using-git-rebase" title="Keeping a patch series up to date using git rebase">the section called “Keeping a patch series up to date using git rebase”</a>). | |
| </li></ul></div> | |
| <p>You may force <code class="literal">git</code> <code class="literal">push</code> to perform the update anyway by preceding the | |
| branch name with a plus sign:</p> | |
| <pre class="screen">$ git push ssh://yourserver.com/~you/proj.git +master</pre> | |
| <p>Note the addition of the <code class="literal">+</code> sign. Alternatively, you can use the | |
| <code class="literal">-f</code> flag to force the remote update, as in:</p> | |
| <pre class="screen">$ git push -f ssh://yourserver.com/~you/proj.git master</pre> | |
| <p>Normally whenever a branch head in a public repository is modified, it | |
| is modified to point to a descendant of the commit that it pointed to | |
| before. By forcing a push in this situation, you break that convention. | |
| (See <a class="xref" href="#problems-With-rewriting-history" title="Problems with rewriting history">the section called “Problems with rewriting history”</a>.)</p> | |
| <p>Nevertheless, this is a common practice for people that need a simple | |
| way to publish a work-in-progress patch series, and it is an acceptable | |
| compromise as long as you warn other developers that this is how you | |
| intend to manage the branch.</p> | |
| <p>It’s also possible for a push to fail in this way when other people have | |
| the right to push to the same repository. In that case, the correct | |
| solution is to retry the push after first updating your work: either by a | |
| pull, or by a fetch followed by a rebase; see the | |
| <a class="link" href="#setting-up-a-shared-repository" title="Setting up a shared repository">next section</a> and | |
| <a class="ulink" href="gitcvs-migration.html" target="_top">gitcvs-migration(7)</a> for more.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="setting-up-a-shared-repository"></a>Setting up a shared repository</h3></div></div></div> | |
| <p>Another way to collaborate is by using a model similar to that | |
| commonly used in CVS, where several developers with special rights | |
| all push to and pull from a single shared repository. See | |
| <a class="ulink" href="gitcvs-migration.html" target="_top">gitcvs-migration(7)</a> for instructions on how to | |
| set this up.</p> | |
| <p>However, while there is nothing wrong with Git’s support for shared | |
| repositories, this mode of operation is not generally recommended, | |
| simply because the mode of collaboration that Git supports—by | |
| exchanging patches and pulling from public repositories—has so many | |
| advantages over the central shared repository:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| Git’s ability to quickly import and merge patches allows a | |
| single maintainer to process incoming changes even at very | |
| high rates. And when that becomes too much, <code class="literal">git</code> <code class="literal">pull</code> provides | |
| an easy way for that maintainer to delegate this job to other | |
| maintainers while still allowing optional review of incoming | |
| changes. | |
| </li><li class="listitem"> | |
| Since every developer’s repository has the same complete copy | |
| of the project history, no repository is special, and it is | |
| trivial for another developer to take over maintenance of a | |
| project, either by mutual agreement, or because a maintainer | |
| becomes unresponsive or difficult to work with. | |
| </li><li class="listitem"> | |
| The lack of a central group of "committers" means there is | |
| less need for formal decisions about who is "in" and who is | |
| "out". | |
| </li></ul></div> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="setting-up-gitweb"></a>Allowing web browsing of a repository</h3></div></div></div> | |
| <p>The gitweb cgi script provides users an easy way to browse your | |
| project’s revisions, file contents and logs without having to install | |
| Git. Features like RSS/Atom feeds and blame/annotation details may | |
| optionally be enabled.</p> | |
| <p>The <a class="ulink" href="git-instaweb.html" target="_top">git-instaweb(1)</a> command provides a simple way to start | |
| browsing the repository using gitweb. The default server when using | |
| instaweb is lighttpd.</p> | |
| <p>See the file gitweb/INSTALL in the Git source tree and | |
| <a class="ulink" href="gitweb.html" target="_top">gitweb(1)</a> for instructions on details setting up a permanent | |
| installation with a CGI or Perl capable server.</p> | |
| </div> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-to-get-a-git-repository-with-minimal-history"></a>How to get a Git repository with minimal history</h2></div></div></div> | |
| <p>A <a class="link" href="#def_shallow_clone">shallow clone</a>, with its truncated | |
| history, is useful when one is interested only in recent history | |
| of a project and getting full history from the upstream is | |
| expensive.</p> | |
| <p>A <a class="link" href="#def_shallow_clone">shallow clone</a> is created by specifying | |
| the <a class="ulink" href="git-clone.html" target="_top">git-clone(1)</a> <code class="literal">--depth</code> switch. The depth can later be | |
| changed with the <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a> <code class="literal">--depth</code> switch, or full | |
| history restored with <code class="literal">--unshallow</code>.</p> | |
| <p>Merging inside a <a class="link" href="#def_shallow_clone">shallow clone</a> will work as long | |
| as a merge base is in the recent history. | |
| Otherwise, it will be like merging unrelated histories and may | |
| have to result in huge conflicts. This limitation may make such | |
| a repository unsuitable to be used in merge based workflows.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sharing-development-examples"></a>Examples</h2></div></div></div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="maintaining-topic-branches"></a>Maintaining topic branches for a Linux subsystem maintainer</h3></div></div></div> | |
| <p>This describes how Tony Luck uses Git in his role as maintainer of the | |
| IA64 architecture for the Linux kernel.</p> | |
| <p>He uses two public branches:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| A "test" tree into which patches are initially placed so that they | |
| can get some exposure when integrated with other ongoing development. | |
| This tree is available to Andrew for pulling into -mm whenever he | |
| wants. | |
| </li><li class="listitem"> | |
| A "release" tree into which tested patches are moved for final sanity | |
| checking, and as a vehicle to send them upstream to Linus (by sending | |
| him a "please pull" request.) | |
| </li></ul></div> | |
| <p>He also uses a set of temporary branches ("topic branches"), each | |
| containing a logical grouping of patches.</p> | |
| <p>To set this up, first create your work tree by cloning Linus’s public | |
| tree:</p> | |
| <pre class="screen">$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git work | |
| $ cd work</pre> | |
| <p>Linus’s tree will be stored in the remote-tracking branch named origin/master, | |
| and can be updated using <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a>; you can track other | |
| public trees using <a class="ulink" href="git-remote.html" target="_top">git-remote(1)</a> to set up a "remote" and | |
| <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a> to keep them up to date; see | |
| <a class="xref" href="#repositories-and-branches" title="Chapter 1. Repositories and Branches">Chapter 1, <i>Repositories and Branches</i></a>.</p> | |
| <p>Now create the branches in which you are going to work; these start out | |
| at the current tip of origin/master branch, and should be set up (using | |
| the <code class="literal">--track</code> option to <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a>) to merge changes in from | |
| Linus by default.</p> | |
| <pre class="screen">$ git branch --track test origin/master | |
| $ git branch --track release origin/master</pre> | |
| <p>These can be easily kept up to date using <a class="ulink" href="git-pull.html" target="_top">git-pull(1)</a>.</p> | |
| <pre class="screen">$ git switch test && git pull | |
| $ git switch release && git pull</pre> | |
| <p>Important note! If you have any local changes in these branches, then | |
| this merge will create a commit object in the history (with no local | |
| changes Git will simply do a "fast-forward" merge). Many people dislike | |
| the "noise" that this creates in the Linux history, so you should avoid | |
| doing this capriciously in the <code class="literal">release</code> branch, as these noisy commits | |
| will become part of the permanent history when you ask Linus to pull | |
| from the release branch.</p> | |
| <p>A few configuration variables (see <a class="ulink" href="git-config.html" target="_top">git-config(1)</a>) can | |
| make it easy to push both branches to your public tree. (See | |
| <a class="xref" href="#setting-up-a-public-repository" title="Setting up a public repository">the section called “Setting up a public repository”</a>.)</p> | |
| <pre class="screen">$ cat >> .git/config <<EOF | |
| [remote "mytree"] | |
| url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux.git | |
| push = release | |
| push = test | |
| EOF</pre> | |
| <p>Then you can push both the test and release trees using | |
| <a class="ulink" href="git-push.html" target="_top">git-push(1)</a>:</p> | |
| <pre class="screen">$ git push mytree</pre> | |
| <p>or push just one of the test and release branches using:</p> | |
| <pre class="screen">$ git push mytree test</pre> | |
| <p>or</p> | |
| <pre class="screen">$ git push mytree release</pre> | |
| <p>Now to apply some patches from the community. Think of a short | |
| snappy name for a branch to hold this patch (or related group of | |
| patches), and create a new branch from a recent stable tag of | |
| Linus’s branch. Picking a stable base for your branch will: | |
| 1) help you: by avoiding inclusion of unrelated and perhaps lightly | |
| tested changes | |
| 2) help future bug hunters that use <code class="literal">git</code> <code class="literal">bisect</code> to find problems</p> | |
| <pre class="screen">$ git switch -c speed-up-spinlocks v2.6.35</pre> | |
| <p>Now you apply the patch(es), run some tests, and commit the change(s). If | |
| the patch is a multi-part series, then you should apply each as a separate | |
| commit to this branch.</p> | |
| <pre class="screen">$ ... patch ... test ... commit [ ... patch ... test ... commit ]*</pre> | |
| <p>When you are happy with the state of this change, you can merge it into the | |
| "test" branch in preparation to make it public:</p> | |
| <pre class="screen">$ git switch test && git merge speed-up-spinlocks</pre> | |
| <p>It is unlikely that you would have any conflicts here … but you might if you | |
| spent a while on this step and had also pulled new versions from upstream.</p> | |
| <p>Sometime later when enough time has passed and testing done, you can pull the | |
| same branch into the <code class="literal">release</code> tree ready to go upstream. This is where you | |
| see the value of keeping each patch (or patch series) in its own branch. It | |
| means that the patches can be moved into the <code class="literal">release</code> tree in any order.</p> | |
| <pre class="screen">$ git switch release && git merge speed-up-spinlocks</pre> | |
| <p>After a while, you will have a number of branches, and despite the | |
| well chosen names you picked for each of them, you may forget what | |
| they are for, or what status they are in. To get a reminder of what | |
| changes are in a specific branch, use:</p> | |
| <pre class="screen">$ git log linux..branchname | git shortlog</pre> | |
| <p>To see whether it has already been merged into the test or release branches, | |
| use:</p> | |
| <pre class="screen">$ git log test..branchname</pre> | |
| <p>or</p> | |
| <pre class="screen">$ git log release..branchname</pre> | |
| <p>(If this branch has not yet been merged, you will see some log entries. | |
| If it has been merged, then there will be no output.)</p> | |
| <p>Once a patch completes the great cycle (moving from test to release, | |
| then pulled by Linus, and finally coming back into your local | |
| <code class="literal">origin/master</code> branch), the branch for this change is no longer needed. | |
| You detect this when the output from:</p> | |
| <pre class="screen">$ git log origin..branchname</pre> | |
| <p>is empty. At this point the branch can be deleted:</p> | |
| <pre class="screen">$ git branch -d branchname</pre> | |
| <p>Some changes are so trivial that it is not necessary to create a separate | |
| branch and then merge into each of the test and release branches. For | |
| these changes, just apply directly to the <code class="literal">release</code> branch, and then | |
| merge that into the <code class="literal">test</code> branch.</p> | |
| <p>After pushing your work to <code class="literal">mytree</code>, you can use | |
| <a class="ulink" href="git-request-pull.html" target="_top">git-request-pull(1)</a> to prepare a "please pull" request message | |
| to send to Linus:</p> | |
| <pre class="screen">$ git push mytree | |
| $ git request-pull origin mytree release</pre> | |
| <p>Here are some of the scripts that simplify all this even further.</p> | |
| <pre class="screen">==== update script ==== | |
| # Update a branch in my Git tree. If the branch to be updated | |
| # is origin, then pull from kernel.org. Otherwise merge | |
| # origin/master branch into test|release branch | |
| case "$1" in | |
| test|release) | |
| git checkout $1 && git pull . origin | |
| ;; | |
| origin) | |
| before=$(git rev-parse refs/remotes/origin/master) | |
| git fetch origin | |
| after=$(git rev-parse refs/remotes/origin/master) | |
| if [ $before != $after ] | |
| then | |
| git log $before..$after | git shortlog | |
| fi | |
| ;; | |
| *) | |
| echo "usage: $0 origin|test|release" 1>&2 | |
| exit 1 | |
| ;; | |
| esac</pre> | |
| <pre class="screen">==== merge script ==== | |
| # Merge a branch into either the test or release branch | |
| pname=$0 | |
| usage() | |
| { | |
| echo "usage: $pname branch test|release" 1>&2 | |
| exit 1 | |
| } | |
| git show-ref -q --verify -- refs/heads/"$1" || { | |
| echo "Can't see branch <$1>" 1>&2 | |
| usage | |
| } | |
| case "$2" in | |
| test|release) | |
| if [ $(git log $2..$1 | wc -c) -eq 0 ] | |
| then | |
| echo $1 already merged into $2 1>&2 | |
| exit 1 | |
| fi | |
| git checkout $2 && git pull . $1 | |
| ;; | |
| *) | |
| usage | |
| ;; | |
| esac</pre> | |
| <pre class="screen">==== status script ==== | |
| # report on status of my ia64 Git tree | |
| gb=$(tput setab 2) | |
| rb=$(tput setab 1) | |
| restore=$(tput setab 9) | |
| if [ `git rev-list test..release | wc -c` -gt 0 ] | |
| then | |
| echo $rb Warning: commits in release that are not in test $restore | |
| git log test..release | |
| fi | |
| for branch in `git show-ref --heads | sed 's|^.*/||'` | |
| do | |
| if [ $branch = test -o $branch = release ] | |
| then | |
| continue | |
| fi | |
| echo -n $gb ======= $branch ====== $restore " " | |
| status= | |
| for ref in test release origin/master | |
| do | |
| if [ `git rev-list $ref..$branch | wc -c` -gt 0 ] | |
| then | |
| status=$status${ref:0:1} | |
| fi | |
| done | |
| case $status in | |
| trl) | |
| echo $rb Need to pull into test $restore | |
| ;; | |
| rl) | |
| echo "In test" | |
| ;; | |
| l) | |
| echo "Waiting for linus" | |
| ;; | |
| "") | |
| echo $rb All done $restore | |
| ;; | |
| *) | |
| echo $rb "<$status>" $restore | |
| ;; | |
| esac | |
| git log origin/master..$branch | git shortlog | |
| done</pre> | |
| </div> | |
| </div> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="cleaning-up-history"></a>Chapter 5. Rewriting history and maintaining patch series</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#patch-series">Creating the perfect patch series</a></span></dt><dt><span class="section"><a href="#using-git-rebase">Keeping a patch series up to date using git rebase</a></span></dt><dt><span class="section"><a href="#rewriting-one-commit">Rewriting a single commit</a></span></dt><dt><span class="section"><a href="#reordering-patch-series">Reordering or selecting from a patch series</a></span></dt><dt><span class="section"><a href="#interactive-rebase">Using interactive rebases</a></span></dt><dt><span class="section"><a href="#patch-series-tools">Other tools</a></span></dt><dt><span class="section"><a href="#problems-With-rewriting-history">Problems with rewriting history</a></span></dt><dt><span class="section"><a href="#bisect-merges">Why bisecting merge commits can be harder than bisecting linear history</a></span></dt></dl></div> | |
| <p>Normally commits are only added to a project, never taken away or | |
| replaced. Git is designed with this assumption, and violating it will | |
| cause Git’s merge machinery (for example) to do the wrong thing.</p> | |
| <p>However, there is a situation in which it can be useful to violate this | |
| assumption.</p> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="patch-series"></a>Creating the perfect patch series</h2></div></div></div> | |
| <p>Suppose you are a contributor to a large project, and you want to add a | |
| complicated feature, and to present it to the other developers in a way | |
| that makes it easy for them to read your changes, verify that they are | |
| correct, and understand why you made each change.</p> | |
| <p>If you present all of your changes as a single patch (or commit), they | |
| may find that it is too much to digest all at once.</p> | |
| <p>If you present them with the entire history of your work, complete with | |
| mistakes, corrections, and dead ends, they may be overwhelmed.</p> | |
| <p>So the ideal is usually to produce a series of patches such that:</p> | |
| <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> | |
| Each patch can be applied in order. | |
| </li><li class="listitem"> | |
| Each patch includes a single logical change, together with a | |
| message explaining the change. | |
| </li><li class="listitem"> | |
| No patch introduces a regression: after applying any initial | |
| part of the series, the resulting project still compiles and | |
| works, and has no bugs that it didn’t have before. | |
| </li><li class="listitem"> | |
| The complete series produces the same end result as your own | |
| (probably much messier!) development process did. | |
| </li></ol></div> | |
| <p>We will introduce some tools that can help you do this, explain how to | |
| use them, and then explain some of the problems that can arise because | |
| you are rewriting history.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="using-git-rebase"></a>Keeping a patch series up to date using git rebase</h2></div></div></div> | |
| <p>Suppose that you create a branch <code class="literal">mywork</code> on a remote-tracking branch | |
| <code class="literal">origin</code>, and create some commits on top of it:</p> | |
| <pre class="screen">$ git switch -c mywork origin | |
| $ vi file.txt | |
| $ git commit | |
| $ vi otherfile.txt | |
| $ git commit | |
| ...</pre> | |
| <p>You have performed no merges into mywork, so it is just a simple linear | |
| sequence of patches on top of <code class="literal">origin</code>:</p> | |
| <pre class="literallayout"> o--o--O <-- origin | |
| \ | |
| a--b--c <-- mywork</pre> | |
| <p>Some more interesting work has been done in the upstream project, and | |
| <code class="literal">origin</code> has advanced:</p> | |
| <pre class="literallayout"> o--o--O--o--o--o <-- origin | |
| \ | |
| a--b--c <-- mywork</pre> | |
| <p>At this point, you could use <code class="literal">pull</code> to merge your changes back in; | |
| the result would create a new merge commit, like this:</p> | |
| <pre class="literallayout"> o--o--O--o--o--o <-- origin | |
| \ \ | |
| a--b--c--m <-- mywork</pre> | |
| <p>However, if you prefer to keep the history in mywork a simple series of | |
| commits without any merges, you may instead choose to use | |
| <a class="ulink" href="git-rebase.html" target="_top">git-rebase(1)</a>:</p> | |
| <pre class="screen">$ git switch mywork | |
| $ git rebase origin</pre> | |
| <p>This will remove each of your commits from mywork, temporarily saving | |
| them as patches (in a directory named .<code class="literal">git/rebase-apply</code>), update mywork to | |
| point at the latest version of origin, then apply each of the saved | |
| patches to the new mywork. The result will look like:</p> | |
| <pre class="literallayout"> o--o--O--o--o--o <-- origin | |
| \ | |
| a'--b'--c' <-- mywork</pre> | |
| <p>In the process, it may discover conflicts. In that case it will stop | |
| and allow you to fix the conflicts; after fixing conflicts, use <code class="literal">git</code> <code class="literal">add</code> | |
| to update the index with those contents, and then, instead of | |
| running <code class="literal">git</code> <code class="literal">commit</code>, just run</p> | |
| <pre class="screen">$ git rebase --continue</pre> | |
| <p>and Git will continue applying the rest of the patches.</p> | |
| <p>At any point you may use the <code class="literal">--abort</code> option to abort this process and | |
| return mywork to the state it had before you started the rebase:</p> | |
| <pre class="screen">$ git rebase --abort</pre> | |
| <p>If you need to reorder or edit a number of commits in a branch, it may | |
| be easier to use <code class="literal">git</code> <code class="literal">rebase</code> <code class="literal">-i</code>, which allows you to reorder and | |
| squash commits, as well as marking them for individual editing during | |
| the rebase. See <a class="xref" href="#interactive-rebase" title="Using interactive rebases">the section called “Using interactive rebases”</a> for details, and | |
| <a class="xref" href="#reordering-patch-series" title="Reordering or selecting from a patch series">the section called “Reordering or selecting from a patch series”</a> for alternatives.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="rewriting-one-commit"></a>Rewriting a single commit</h2></div></div></div> | |
| <p>We saw in <a class="xref" href="#fixing-a-mistake-by-rewriting-history" title="Fixing a mistake by rewriting history">the section called “Fixing a mistake by rewriting history”</a> that you can replace the | |
| most recent commit using</p> | |
| <pre class="screen">$ git commit --amend</pre> | |
| <p>which will replace the old commit by a new commit incorporating your | |
| changes, giving you a chance to edit the old commit message first. | |
| This is useful for fixing typos in your last commit, or for adjusting | |
| the patch contents of a poorly staged commit.</p> | |
| <p>If you need to amend commits from deeper in your history, you can | |
| use <a class="link" href="#interactive-rebase" title="Using interactive rebases">interactive rebase’s <code class="literal">edit</code> instruction</a>.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="reordering-patch-series"></a>Reordering or selecting from a patch series</h2></div></div></div> | |
| <p>Sometimes you want to edit a commit deeper in your history. One | |
| approach is to use <code class="literal">git</code> <code class="literal">format-patch</code> to create a series of patches | |
| and then reset the state to before the patches:</p> | |
| <pre class="screen">$ git format-patch origin | |
| $ git reset --hard origin</pre> | |
| <p>Then modify, reorder, or eliminate patches as needed before applying | |
| them again with <a class="ulink" href="git-am.html" target="_top">git-am(1)</a>:</p> | |
| <pre class="screen">$ git am *.patch</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="interactive-rebase"></a>Using interactive rebases</h2></div></div></div> | |
| <p>You can also edit a patch series with an interactive rebase. This is | |
| the same as <a class="link" href="#reordering-patch-series" title="Reordering or selecting from a patch series">reordering a patch series using | |
| <code class="literal">format-patch</code></a>, so use whichever interface you like best.</p> | |
| <p>Rebase your current HEAD on the last commit you want to retain as-is. | |
| For example, if you want to reorder the last 5 commits, use:</p> | |
| <pre class="screen">$ git rebase -i HEAD~5</pre> | |
| <p>This will open your editor with a list of steps to be taken to perform | |
| your rebase.</p> | |
| <pre class="screen">pick deadbee The oneline of this commit | |
| pick fa1afe1 The oneline of the next commit | |
| ... | |
| # Rebase c0ffeee..deadbee onto c0ffeee | |
| # | |
| # Commands: | |
| # p, pick = use commit | |
| # r, reword = use commit, but edit the commit message | |
| # e, edit = use commit, but stop for amending | |
| # s, squash = use commit, but meld into previous commit | |
| # f, fixup = like "squash", but discard this commit's log message | |
| # x, exec = run command (the rest of the line) using shell | |
| # | |
| # These lines can be re-ordered; they are executed from top to bottom. | |
| # | |
| # If you remove a line here THAT COMMIT WILL BE LOST. | |
| # | |
| # However, if you remove everything, the rebase will be aborted. | |
| # | |
| # Note that empty commits are commented out</pre> | |
| <p>As explained in the comments, you can reorder commits, squash them | |
| together, edit commit messages, etc. by editing the list. Once you | |
| are satisfied, save the list and close your editor, and the rebase | |
| will begin.</p> | |
| <p>The rebase will stop where <code class="literal">pick</code> has been replaced with <code class="literal">edit</code> or | |
| when a step in the list fails to mechanically resolve conflicts and | |
| needs your help. When you are done editing and/or resolving conflicts | |
| you can continue with <code class="literal">git</code> <code class="literal">rebase</code> <code class="literal">--continue</code>. If you decide that | |
| things are getting too hairy, you can always bail out with <code class="literal">git</code> <code class="literal">rebase</code> | |
| <code class="literal">--abort</code>. Even after the rebase is complete, you can still recover | |
| the original branch by using the <a class="link" href="#reflogs" title="Reflogs">reflog</a>.</p> | |
| <p>For a more detailed discussion of the procedure and additional tips, | |
| see the "INTERACTIVE MODE" section of <a class="ulink" href="git-rebase.html" target="_top">git-rebase(1)</a>.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="patch-series-tools"></a>Other tools</h2></div></div></div> | |
| <p>There are numerous other tools, such as StGit, which exist for the | |
| purpose of maintaining a patch series. These are outside of the scope of | |
| this manual.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="problems-With-rewriting-history"></a>Problems with rewriting history</h2></div></div></div> | |
| <p>The primary problem with rewriting the history of a branch has to do | |
| with merging. Suppose somebody fetches your branch and merges it into | |
| their branch, with a result something like this:</p> | |
| <pre class="literallayout"> o--o--O--o--o--o <-- origin | |
| \ \ | |
| t--t--t--m <-- their branch:</pre> | |
| <p>Then suppose you modify the last three commits:</p> | |
| <pre class="literallayout"> o--o--o <-- new head of origin | |
| / | |
| o--o--O--o--o--o <-- old head of origin</pre> | |
| <p>If we examined all this history together in one repository, it will | |
| look like:</p> | |
| <pre class="literallayout"> o--o--o <-- new head of origin | |
| / | |
| o--o--O--o--o--o <-- old head of origin | |
| \ \ | |
| t--t--t--m <-- their branch:</pre> | |
| <p>Git has no way of knowing that the new head is an updated version of | |
| the old head; it treats this situation exactly the same as it would if | |
| two developers had independently done the work on the old and new heads | |
| in parallel. At this point, if someone attempts to merge the new head | |
| in to their branch, Git will attempt to merge together the two (old and | |
| new) lines of development, instead of trying to replace the old by the | |
| new. The results are likely to be unexpected.</p> | |
| <p>You may still choose to publish branches whose history is rewritten, | |
| and it may be useful for others to be able to fetch those branches in | |
| order to examine or test them, but they should not attempt to pull such | |
| branches into their own work.</p> | |
| <p>For true distributed development that supports proper merging, | |
| published branches should never be rewritten.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="bisect-merges"></a>Why bisecting merge commits can be harder than bisecting linear history</h2></div></div></div> | |
| <p>The <a class="ulink" href="git-bisect.html" target="_top">git-bisect(1)</a> command correctly handles history that | |
| includes merge commits. However, when the commit that it finds is a | |
| merge commit, the user may need to work harder than usual to figure out | |
| why that commit introduced a problem.</p> | |
| <p>Imagine this history:</p> | |
| <pre class="literallayout"> ---Z---o---X---...---o---A---C---D | |
| \ / | |
| o---o---Y---...---o---B</pre> | |
| <p>Suppose that on the upper line of development, the meaning of one | |
| of the functions that exists at Z is changed at commit X. The | |
| commits from Z leading to A change both the function’s | |
| implementation and all calling sites that exist at Z, as well | |
| as new calling sites they add, to be consistent. There is no | |
| bug at A.</p> | |
| <p>Suppose that in the meantime on the lower line of development somebody | |
| adds a new calling site for that function at commit Y. The | |
| commits from Z leading to B all assume the old semantics of that | |
| function and the callers and the callee are consistent with each | |
| other. There is no bug at B, either.</p> | |
| <p>Suppose further that the two development lines merge cleanly at C, | |
| so no conflict resolution is required.</p> | |
| <p>Nevertheless, the code at C is broken, because the callers added | |
| on the lower line of development have not been converted to the new | |
| semantics introduced on the upper line of development. So if all | |
| you know is that D is bad, that Z is good, and that | |
| <a class="ulink" href="git-bisect.html" target="_top">git-bisect(1)</a> identifies C as the culprit, how will you | |
| figure out that the problem is due to this change in semantics?</p> | |
| <p>When the result of a <code class="literal">git</code> <code class="literal">bisect</code> is a non-merge commit, you should | |
| normally be able to discover the problem by examining just that commit. | |
| Developers can make this easy by breaking their changes into small | |
| self-contained commits. That won’t help in the case above, however, | |
| because the problem isn’t obvious from examination of any single | |
| commit; instead, a global view of the development is required. To | |
| make matters worse, the change in semantics in the problematic | |
| function may be just one small part of the changes in the upper | |
| line of development.</p> | |
| <p>On the other hand, if instead of merging at C you had rebased the | |
| history between Z to B on top of A, you would have gotten this | |
| linear history:</p> | |
| <pre class="literallayout"> ---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D*</pre> | |
| <p>Bisecting between Z and D* would hit a single culprit commit Y*, | |
| and understanding why Y* was broken would probably be easier.</p> | |
| <p>Partly for this reason, many experienced Git users, even when | |
| working on an otherwise merge-heavy project, keep the history | |
| linear by rebasing against the latest upstream version before | |
| publishing.</p> | |
| </div> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="advanced-branch-management"></a>Chapter 6. Advanced branch management</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#fetching-individual-branches">Fetching individual branches</a></span></dt><dt><span class="section"><a href="#fetch-fast-forwards">git fetch and fast-forwards</a></span></dt><dt><span class="section"><a href="#forcing-fetch">Forcing git fetch to do non-fast-forward updates</a></span></dt><dt><span class="section"><a href="#remote-branch-configuration">Configuring remote-tracking branches</a></span></dt></dl></div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fetching-individual-branches"></a>Fetching individual branches</h2></div></div></div> | |
| <p>Instead of using <a class="ulink" href="git-remote.html" target="_top">git-remote(1)</a>, you can also choose just | |
| to update one branch at a time, and to store it locally under an | |
| arbitrary name:</p> | |
| <pre class="screen">$ git fetch origin todo:my-todo-work</pre> | |
| <p>The first argument, <code class="literal">origin</code>, just tells Git to fetch from the | |
| repository you originally cloned from. The second argument tells Git | |
| to fetch the branch named <code class="literal">todo</code> from the remote repository, and to | |
| store it locally under the name <code class="literal">refs/heads/my-todo-work</code>.</p> | |
| <p>You can also fetch branches from other repositories; so</p> | |
| <pre class="screen">$ git fetch git://example.com/proj.git master:example-master</pre> | |
| <p>will create a new branch named <code class="literal">example-master</code> and store in it the | |
| branch named <code class="literal">master</code> from the repository at the given URL. If you | |
| already have a branch named example-master, it will attempt to | |
| <a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a> to the commit given by example.com’s | |
| master branch. In more detail:</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fetch-fast-forwards"></a>git fetch and fast-forwards</h2></div></div></div> | |
| <p>In the previous example, when updating an existing branch, <code class="literal">git</code> <code class="literal">fetch</code> | |
| checks to make sure that the most recent commit on the remote | |
| branch is a descendant of the most recent commit on your copy of the | |
| branch before updating your copy of the branch to point at the new | |
| commit. Git calls this process a <a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a>.</p> | |
| <p>A fast-forward looks something like this:</p> | |
| <pre class="literallayout"> o--o--o--o <-- old head of the branch | |
| \ | |
| o--o--o <-- new head of the branch</pre> | |
| <p>In some cases it is possible that the new head will <span class="strong"><strong>not</strong></span> actually be | |
| a descendant of the old head. For example, the developer may have | |
| realized a serious mistake was made and decided to backtrack, | |
| resulting in a situation like:</p> | |
| <pre class="literallayout"> o--o--o--o--a--b <-- old head of the branch | |
| \ | |
| o--o--o <-- new head of the branch</pre> | |
| <p>In this case, <code class="literal">git</code> <code class="literal">fetch</code> will fail, and print out a warning.</p> | |
| <p>In that case, you can still force Git to update to the new head, as | |
| described in the following section. However, note that in the | |
| situation above this may mean losing the commits labeled <code class="literal">a</code> and <code class="literal">b</code>, | |
| unless you’ve already created a reference of your own pointing to | |
| them.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="forcing-fetch"></a>Forcing git fetch to do non-fast-forward updates</h2></div></div></div> | |
| <p>If git fetch fails because the new head of a branch is not a | |
| descendant of the old head, you may force the update with:</p> | |
| <pre class="screen">$ git fetch git://example.com/proj.git +master:refs/remotes/example/master</pre> | |
| <p>Note the addition of the <code class="literal">+</code> sign. Alternatively, you can use the <code class="literal">-f</code> | |
| flag to force updates of all the fetched branches, as in:</p> | |
| <pre class="screen">$ git fetch -f origin</pre> | |
| <p>Be aware that commits that the old version of example/master pointed at | |
| may be lost, as we saw in the previous section.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="remote-branch-configuration"></a>Configuring remote-tracking branches</h2></div></div></div> | |
| <p>We saw above that <code class="literal">origin</code> is just a shortcut to refer to the | |
| repository that you originally cloned from. This information is | |
| stored in Git configuration variables, which you can see using | |
| <a class="ulink" href="git-config.html" target="_top">git-config(1)</a>:</p> | |
| <pre class="screen">$ git config list | |
| core.repositoryformatversion=0 | |
| core.filemode=true | |
| core.logallrefupdates=true | |
| remote.origin.url=git://git.kernel.org/pub/scm/git/git.git | |
| remote.origin.fetch=+refs/heads/*:refs/remotes/origin/* | |
| branch.master.remote=origin | |
| branch.master.merge=refs/heads/master</pre> | |
| <p>If there are other repositories that you also use frequently, you can | |
| create similar configuration options to save typing; for example,</p> | |
| <pre class="screen">$ git remote add example git://example.com/proj.git</pre> | |
| <p>adds the following to .<code class="literal">git/config</code>:</p> | |
| <pre class="screen">[remote "example"] | |
| url = git://example.com/proj.git | |
| fetch = +refs/heads/*:refs/remotes/example/*</pre> | |
| <p>Also note that the above configuration can be performed by directly | |
| editing the file .<code class="literal">git/config</code> instead of using <a class="ulink" href="git-remote.html" target="_top">git-remote(1)</a>.</p> | |
| <p>After configuring the remote, the following three commands will do the | |
| same thing:</p> | |
| <pre class="screen">$ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/* | |
| $ git fetch example +refs/heads/*:refs/remotes/example/* | |
| $ git fetch example</pre> | |
| <p>See <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for more details on the configuration | |
| options mentioned above and <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a> for more details on | |
| the refspec syntax.</p> | |
| </div> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="git-concepts"></a>Chapter 7. Git concepts</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#the-object-database">The Object Database</a></span></dt><dd><dl><dt><span class="section"><a href="#commit-object">Commit Object</a></span></dt><dt><span class="section"><a href="#tree-object">Tree Object</a></span></dt><dt><span class="section"><a href="#blob-object">Blob Object</a></span></dt><dt><span class="section"><a href="#trust">Trust</a></span></dt><dt><span class="section"><a href="#tag-object">Tag Object</a></span></dt><dt><span class="section"><a href="#pack-files">How Git stores objects efficiently: pack files</a></span></dt><dt><span class="section"><a href="#dangling-objects">Dangling objects</a></span></dt><dt><span class="section"><a href="#recovering-from-repository-corruption">Recovering from repository corruption</a></span></dt></dl></dd><dt><span class="section"><a href="#the-index">The index</a></span></dt></dl></div> | |
| <p>Git is built on a small number of simple but powerful ideas. While it | |
| is possible to get things done without understanding them, you will find | |
| Git much more intuitive if you do.</p> | |
| <p>We start with the most important, the <a class="link" href="#def_object_database">object | |
| database</a> and the <a class="link" href="#def_index">index</a>.</p> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="the-object-database"></a>The Object Database</h2></div></div></div> | |
| <p>We already saw in <a class="xref" href="#understanding-commits" title="Understanding History: Commits">the section called “Understanding History: Commits”</a> that all commits are stored | |
| under a 40-digit "object name". In fact, all the information needed to | |
| represent the history of a project is stored in objects with such names. | |
| In each case the name is calculated by taking the SHA-1 hash of the | |
| contents of the object. The SHA-1 hash is a cryptographic hash function. | |
| What that means to us is that it is impossible to find two different | |
| objects with the same name. This has a number of advantages; among | |
| others:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| Git can quickly determine whether two objects are identical or not, | |
| just by comparing names. | |
| </li><li class="listitem"> | |
| Since object names are computed the same way in every repository, the | |
| same content stored in two repositories will always be stored under | |
| the same name. | |
| </li><li class="listitem"> | |
| Git can detect errors when it reads an object, by checking that the | |
| object’s name is still the SHA-1 hash of its contents. | |
| </li></ul></div> | |
| <p>(See <a class="xref" href="#object-details" title="Object storage format">the section called “Object storage format”</a> for the details of the object formatting and | |
| SHA-1 calculation.)</p> | |
| <p>There are four different types of objects: "blob", "tree", "commit", and | |
| "tag".</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| A <a class="link" href="#def_blob_object">"blob" object</a> is used to store file data. | |
| </li><li class="listitem"> | |
| A <a class="link" href="#def_tree_object">"tree" object</a> ties one or more | |
| "blob" objects into a directory structure. In addition, a tree object | |
| can refer to other tree objects, thus creating a directory hierarchy. | |
| </li><li class="listitem"> | |
| A <a class="link" href="#def_commit_object">"commit" object</a> ties such directory hierarchies | |
| together into a <a class="link" href="#def_DAG">directed acyclic graph</a> of revisions—each | |
| commit contains the object name of exactly one tree designating the | |
| directory hierarchy at the time of the commit. In addition, a commit | |
| refers to "parent" commit objects that describe the history of how we | |
| arrived at that directory hierarchy. | |
| </li><li class="listitem"> | |
| A <a class="link" href="#def_tag_object">"tag" object</a> symbolically identifies and can be | |
| used to sign other objects. It contains the object name and type of | |
| another object, a symbolic name (of course!) and, optionally, a | |
| signature. | |
| </li></ul></div> | |
| <p>The object types in some more detail:</p> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="commit-object"></a>Commit Object</h3></div></div></div> | |
| <p>The "commit" object links a physical state of a tree with a description | |
| of how we got there and why. Use the <code class="literal">--pretty=raw</code> option to | |
| <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> or <a class="ulink" href="git-log.html" target="_top">git-log(1)</a> to examine your favorite | |
| commit:</p> | |
| <pre class="screen">$ git show -s --pretty=raw 2be7fcb476 | |
| commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4 | |
| tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf | |
| parent 257a84d9d02e90447b149af58b271c19405edb6a | |
| author Dave Watson <dwatson@mimvista.com> 1187576872 -0400 | |
| committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700 | |
| Fix misspelling of 'suppress' in docs | |
| Signed-off-by: Junio C Hamano <gitster@pobox.com></pre> | |
| <p>As you can see, a commit is defined by:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| a tree: The SHA-1 name of a tree object (as defined below), representing | |
| the contents of a directory at a certain point in time. | |
| </li><li class="listitem"> | |
| parent(s): The SHA-1 name(s) of some number of commits which represent the | |
| immediately previous step(s) in the history of the project. The | |
| example above has one parent; merge commits may have more than | |
| one. A commit with no parents is called a "root" commit, and | |
| represents the initial revision of a project. Each project must have | |
| at least one root. A project can also have multiple roots, though | |
| that isn’t common (or necessarily a good idea). | |
| </li><li class="listitem"> | |
| an author: The name of the person responsible for this change, together | |
| with its date. | |
| </li><li class="listitem"> | |
| a committer: The name of the person who actually created the commit, | |
| with the date it was done. This may be different from the author, for | |
| example, if the author was someone who wrote a patch and emailed it | |
| to the person who used it to create the commit. | |
| </li><li class="listitem"> | |
| a comment describing this commit. | |
| </li></ul></div> | |
| <p>Note that a commit does not itself contain any information about what | |
| actually changed; all changes are calculated by comparing the contents | |
| of the tree referred to by this commit with the trees associated with | |
| its parents. In particular, Git does not attempt to record file renames | |
| explicitly, though it can identify cases where the existence of the same | |
| file data at changing paths suggests a rename. (See, for example, the | |
| <code class="literal">-M</code> option to <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a>).</p> | |
| <p>A commit is usually created by <a class="ulink" href="git-commit.html" target="_top">git-commit(1)</a>, which creates a | |
| commit whose parent is normally the current HEAD, and whose tree is | |
| taken from the content currently stored in the index.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="tree-object"></a>Tree Object</h3></div></div></div> | |
| <p>The ever-versatile <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> command can also be used to | |
| examine tree objects, but <a class="ulink" href="git-ls-tree.html" target="_top">git-ls-tree(1)</a> will give you more | |
| details:</p> | |
| <pre class="screen">$ git ls-tree fb3a8bdd0ce | |
| 100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore | |
| 100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap | |
| 100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING | |
| 040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation | |
| 100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN | |
| 100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL | |
| 100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile | |
| 100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README | |
| ...</pre> | |
| <p>As you can see, a tree object contains a list of entries, each with a | |
| mode, object type, SHA-1 name, and name, sorted by name. It represents | |
| the contents of a single directory tree.</p> | |
| <p>The object type may be a blob, representing the contents of a file, or | |
| another tree, representing the contents of a subdirectory. Since trees | |
| and blobs, like all other objects, are named by the SHA-1 hash of their | |
| contents, two trees have the same SHA-1 name if and only if their | |
| contents (including, recursively, the contents of all subdirectories) | |
| are identical. This allows Git to quickly determine the differences | |
| between two related tree objects, since it can ignore any entries with | |
| identical object names.</p> | |
| <p>(Note: in the presence of submodules, trees may also have commits as | |
| entries. See <a class="xref" href="#submodules" title="Chapter 8. Submodules">Chapter 8, <i>Submodules</i></a> for documentation.)</p> | |
| <p>Note that the files all have mode 644 or 755: Git actually only pays | |
| attention to the executable bit.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="blob-object"></a>Blob Object</h3></div></div></div> | |
| <p>You can use <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> to examine the contents of a blob; take, | |
| for example, the blob in the entry for <code class="literal">COPYING</code> from the tree above:</p> | |
| <pre class="screen">$ git show 6ff87c4664 | |
| Note that the only valid version of the GPL as far as this project | |
| is concerned is _this_ particular version of the license (ie v2, not | |
| v2.2 or v3.x or whatever), unless explicitly otherwise stated. | |
| ...</pre> | |
| <p>A "blob" object is nothing but a binary blob of data. It doesn’t refer | |
| to anything else or have attributes of any kind.</p> | |
| <p>Since the blob is entirely defined by its data, if two files in a | |
| directory tree (or in multiple different versions of the repository) | |
| have the same contents, they will share the same blob object. The object | |
| is totally independent of its location in the directory tree, and | |
| renaming a file does not change the object that file is associated with.</p> | |
| <p>Note that any tree or blob object can be examined using | |
| <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> with the <revision>:<path> syntax. This can | |
| sometimes be useful for browsing the contents of a tree that is not | |
| currently checked out.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="trust"></a>Trust</h3></div></div></div> | |
| <p>If you receive the SHA-1 name of a blob from one source, and its contents | |
| from another (possibly untrusted) source, you can still trust that those | |
| contents are correct as long as the SHA-1 name agrees. This is because | |
| the SHA-1 is designed so that it is infeasible to find different contents | |
| that produce the same hash.</p> | |
| <p>Similarly, you need only trust the SHA-1 name of a top-level tree object | |
| to trust the contents of the entire directory that it refers to, and if | |
| you receive the SHA-1 name of a commit from a trusted source, then you | |
| can easily verify the entire history of commits reachable through | |
| parents of that commit, and all of those contents of the trees referred | |
| to by those commits.</p> | |
| <p>So to introduce some real trust in the system, the only thing you need | |
| to do is to digitally sign just <span class="emphasis"><em>one</em></span> special note, which includes the | |
| name of a top-level commit. Your digital signature shows others | |
| that you trust that commit, and the immutability of the history of | |
| commits tells others that they can trust the whole history.</p> | |
| <p>In other words, you can easily validate a whole archive by just | |
| sending out a single email that tells the people the name (SHA-1 hash) | |
| of the top commit, and digitally sign that email using something | |
| like GPG/PGP.</p> | |
| <p>To assist in this, Git also provides the tag object…</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="tag-object"></a>Tag Object</h3></div></div></div> | |
| <p>A tag object contains an object, object type, tag name, the name of the | |
| person ("tagger") who created the tag, and a message, which may contain | |
| a signature, as can be seen using <a class="ulink" href="git-cat-file.html" target="_top">git-cat-file(1)</a>:</p> | |
| <pre class="screen">$ git cat-file tag v1.5.0 | |
| object 437b1b20df4b356c9342dac8d38849f24ef44f27 | |
| type commit | |
| tag v1.5.0 | |
| tagger Junio C Hamano <junkio@cox.net> 1171411200 +0000 | |
| GIT 1.5.0 | |
| -----BEGIN PGP SIGNATURE----- | |
| Version: GnuPG v1.4.6 (GNU/Linux) | |
| iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui | |
| nLE/L9aUXdWeTFPron96DLA= | |
| =2E+0 | |
| -----END PGP SIGNATURE-----</pre> | |
| <p>See the <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> command to learn how to create and verify tag | |
| objects. (Note that <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> can also be used to create | |
| "lightweight tags", which are not tag objects at all, but just simple | |
| references whose names begin with <code class="literal">refs/tags/</code>).</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="pack-files"></a>How Git stores objects efficiently: pack files</h3></div></div></div> | |
| <p>Newly created objects are initially created in a file named after the | |
| object’s SHA-1 hash (stored in .<code class="literal">git/objects</code>).</p> | |
| <p>Unfortunately this system becomes inefficient once a project has a | |
| lot of objects. Try this on an old project:</p> | |
| <pre class="screen">$ git count-objects | |
| 6930 objects, 47620 kilobytes</pre> | |
| <p>The first number is the number of objects which are kept in | |
| individual files. The second is the amount of space taken up by | |
| those "loose" objects.</p> | |
| <p>You can save space and make Git faster by moving these loose objects in | |
| to a "pack file", which stores a group of objects in an efficient | |
| compressed format; the details of how pack files are formatted can be | |
| found in <a class="ulink" href="gitformat-pack.html" target="_top">gitformat-pack(5)</a>.</p> | |
| <p>To put the loose objects into a pack, just run git repack:</p> | |
| <pre class="screen">$ git repack | |
| Counting objects: 6020, done. | |
| Delta compression using up to 4 threads. | |
| Compressing objects: 100% (6020/6020), done. | |
| Writing objects: 100% (6020/6020), done. | |
| Total 6020 (delta 4070), reused 0 (delta 0)</pre> | |
| <p>This creates a single "pack file" in .git/objects/pack/ | |
| containing all currently unpacked objects. You can then run</p> | |
| <pre class="screen">$ git prune</pre> | |
| <p>to remove any of the "loose" objects that are now contained in the | |
| pack. This will also remove any unreferenced objects (which may be | |
| created when, for example, you use <code class="literal">git</code> <code class="literal">reset</code> to remove a commit). | |
| You can verify that the loose objects are gone by looking at the | |
| .<code class="literal">git/objects</code> directory or by running</p> | |
| <pre class="screen">$ git count-objects | |
| 0 objects, 0 kilobytes</pre> | |
| <p>Although the object files are gone, any commands that refer to those | |
| objects will work exactly as they did before.</p> | |
| <p>The <a class="ulink" href="git-gc.html" target="_top">git-gc(1)</a> command performs packing, pruning, and more for | |
| you, so is normally the only high-level command you need.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="dangling-objects"></a>Dangling objects</h3></div></div></div> | |
| <p>The <a class="ulink" href="git-fsck.html" target="_top">git-fsck(1)</a> command will sometimes complain about dangling | |
| objects. They are not a problem.</p> | |
| <p>The most common cause of dangling objects is that you’ve rebased a | |
| branch, or you have pulled from somebody else who rebased a branch—see | |
| <a class="xref" href="#cleaning-up-history" title="Chapter 5. Rewriting history and maintaining patch series">Chapter 5, <i>Rewriting history and maintaining patch series</i></a>. In that case, the old head of the original | |
| branch still exists, as does everything it pointed to. The branch | |
| pointer itself just doesn’t, since you replaced it with another one.</p> | |
| <p>There are also other situations that cause dangling objects. For | |
| example, a "dangling blob" may arise because you did a <code class="literal">git</code> <code class="literal">add</code> of a | |
| file, but then, before you actually committed it and made it part of the | |
| bigger picture, you changed something else in that file and committed | |
| that <span class="strong"><strong>updated</strong></span> thing—the old state that you added originally ends up | |
| not being pointed to by any commit or tree, so it’s now a dangling blob | |
| object.</p> | |
| <p>Similarly, when the "ort" merge strategy runs, and finds that | |
| there are criss-cross merges and thus more than one merge base (which is | |
| fairly unusual, but it does happen), it will generate one temporary | |
| midway tree (or possibly even more, if you had lots of criss-crossing | |
| merges and more than two merge bases) as a temporary internal merge | |
| base, and again, those are real objects, but the end result will not end | |
| up pointing to them, so they end up "dangling" in your repository.</p> | |
| <p>Generally, dangling objects aren’t anything to worry about. They can | |
| even be very useful: if you screw something up, the dangling objects can | |
| be how you recover your old tree (say, you did a rebase, and realized | |
| that you really didn’t want to—you can look at what dangling objects | |
| you have, and decide to reset your head to some old dangling state).</p> | |
| <p>For commits, you can just use:</p> | |
| <pre class="screen">$ gitk <dangling-commit-sha-goes-here> --not --all</pre> | |
| <p>This asks for all the history reachable from the given commit but not | |
| from any branch, tag, or other reference. If you decide it’s something | |
| you want, you can always create a new reference to it, e.g.,</p> | |
| <pre class="screen">$ git branch recovered-branch <dangling-commit-sha-goes-here></pre> | |
| <p>For blobs and trees, you can’t do the same, but you can still examine | |
| them. You can just do</p> | |
| <pre class="screen">$ git show <dangling-blob/tree-sha-goes-here></pre> | |
| <p>to show what the contents of the blob were (or, for a tree, basically | |
| what the <code class="literal">ls</code> for that directory was), and that may give you some idea | |
| of what the operation was that left that dangling object.</p> | |
| <p>Usually, dangling blobs and trees aren’t very interesting. They’re | |
| almost always the result of either being a half-way mergebase (the blob | |
| will often even have the conflict markers from a merge in it, if you | |
| have had conflicting merges that you fixed up by hand), or simply | |
| because you interrupted a <code class="literal">git</code> <code class="literal">fetch</code> with ^C or something like that, | |
| leaving <span class="emphasis"><em>some</em></span> of the new objects in the object database, but just | |
| dangling and useless.</p> | |
| <p>Anyway, once you are sure that you’re not interested in any dangling | |
| state, you can just prune all unreachable objects:</p> | |
| <pre class="screen">$ git prune</pre> | |
| <p>and they’ll be gone. (You should only run <code class="literal">git</code> <code class="literal">prune</code> on a quiescent | |
| repository—it’s kind of like doing a filesystem fsck recovery: you | |
| don’t want to do that while the filesystem is mounted. | |
| <code class="literal">git</code> <code class="literal">prune</code> is designed not to cause any harm in such cases of concurrent | |
| accesses to a repository but you might receive confusing or scary messages.)</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="recovering-from-repository-corruption"></a>Recovering from repository corruption</h3></div></div></div> | |
| <p>By design, Git treats data trusted to it with caution. However, even in | |
| the absence of bugs in Git itself, it is still possible that hardware or | |
| operating system errors could corrupt data.</p> | |
| <p>The first defense against such problems is backups. You can back up a | |
| Git directory using clone, or just using cp, tar, or any other backup | |
| mechanism.</p> | |
| <p>As a last resort, you can search for the corrupted objects and attempt | |
| to replace them by hand. Back up your repository before attempting this | |
| in case you corrupt things even more in the process.</p> | |
| <p>We’ll assume that the problem is a single missing or corrupted blob, | |
| which is sometimes a solvable problem. (Recovering missing trees and | |
| especially commits is <span class="strong"><strong>much</strong></span> harder).</p> | |
| <p>Before starting, verify that there is corruption, and figure out where | |
| it is with <a class="ulink" href="git-fsck.html" target="_top">git-fsck(1)</a>; this may be time-consuming.</p> | |
| <p>Assume the output looks like this:</p> | |
| <pre class="screen">$ git fsck --full --no-dangling | |
| broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 | |
| to blob 4b9458b3786228369c63936db65827de3cc06200 | |
| missing blob 4b9458b3786228369c63936db65827de3cc06200</pre> | |
| <p>Now you know that blob 4b9458b3 is missing, and that the tree 2d9263c6 | |
| points to it. If you could find just one copy of that missing blob | |
| object, possibly in some other repository, you could move it into | |
| .<code class="literal">git/objects/4b/9458b3..</code>. and be done. Suppose you can’t. You can | |
| still examine the tree that pointed to it with <a class="ulink" href="git-ls-tree.html" target="_top">git-ls-tree(1)</a>, | |
| which might output something like:</p> | |
| <pre class="screen">$ git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8 | |
| 100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8 .gitignore | |
| 100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883 .mailmap | |
| 100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c COPYING | |
| ... | |
| 100644 blob 4b9458b3786228369c63936db65827de3cc06200 myfile | |
| ...</pre> | |
| <p>So now you know that the missing blob was the data for a file named | |
| <code class="literal">myfile</code>. And chances are you can also identify the directory—let’s | |
| say it’s in <code class="literal">somedirectory</code>. If you’re lucky the missing copy might be | |
| the same as the copy you have checked out in your working tree at | |
| <code class="literal">somedirectory/myfile</code>; you can test whether that’s right with | |
| <a class="ulink" href="git-hash-object.html" target="_top">git-hash-object(1)</a>:</p> | |
| <pre class="screen">$ git hash-object -w somedirectory/myfile</pre> | |
| <p>which will create and store a blob object with the contents of | |
| somedirectory/myfile, and output the SHA-1 of that object. if you’re | |
| extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in | |
| which case you’ve guessed right, and the corruption is fixed!</p> | |
| <p>Otherwise, you need more information. How do you tell which version of | |
| the file has been lost?</p> | |
| <p>The easiest way to do this is with:</p> | |
| <pre class="screen">$ git log --raw --all --full-history -- somedirectory/myfile</pre> | |
| <p>Because you’re asking for raw output, you’ll now get something like</p> | |
| <pre class="screen">commit abc | |
| Author: | |
| Date: | |
| ... | |
| :100644 100644 4b9458b newsha M somedirectory/myfile | |
| commit xyz | |
| Author: | |
| Date: | |
| ... | |
| :100644 100644 oldsha 4b9458b M somedirectory/myfile</pre> | |
| <p>This tells you that the immediately following version of the file was | |
| "newsha", and that the immediately preceding version was "oldsha". | |
| You also know the commit messages that went with the change from oldsha | |
| to 4b9458b and with the change from 4b9458b to newsha.</p> | |
| <p>If you’ve been committing small enough changes, you may now have a good | |
| shot at reconstructing the contents of the in-between state 4b9458b.</p> | |
| <p>If you can do that, you can now recreate the missing object with</p> | |
| <pre class="screen">$ git hash-object -w <recreated-file></pre> | |
| <p>and your repository is good again!</p> | |
| <p>(Btw, you could have ignored the <code class="literal">fsck</code>, and started with doing a</p> | |
| <pre class="screen">$ git log --raw --all</pre> | |
| <p>and just looked for the sha of the missing object (4b9458b) in that | |
| whole thing. It’s up to you—Git does <span class="strong"><strong>have</strong></span> a lot of information, it is | |
| just missing one particular blob version.</p> | |
| </div> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="the-index"></a>The index</h2></div></div></div> | |
| <p>The index is a binary file (generally kept in .<code class="literal">git/index</code>) containing a | |
| sorted list of path names, each with permissions and the SHA-1 of a blob | |
| object; <a class="ulink" href="git-ls-files.html" target="_top">git-ls-files(1)</a> can show you the contents of the index:</p> | |
| <pre class="screen">$ git ls-files --stage | |
| 100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0 .gitignore | |
| 100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0 .mailmap | |
| 100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0 COPYING | |
| 100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0 Documentation/.gitignore | |
| 100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0 Documentation/Makefile | |
| ... | |
| 100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0 xdiff/xtypes.h | |
| 100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0 xdiff/xutils.c | |
| 100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0 xdiff/xutils.h</pre> | |
| <p>Note that in older documentation you may see the index called the | |
| "current directory cache" or just the "cache". It has three important | |
| properties:</p> | |
| <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> | |
| <p class="simpara">The index contains all the information necessary to generate a single | |
| (uniquely determined) tree object.</p> | |
| <p class="simpara">For example, running <a class="ulink" href="git-commit.html" target="_top">git-commit(1)</a> generates this tree object | |
| from the index, stores it in the object database, and uses it as the | |
| tree object associated with the new commit.</p> | |
| </li><li class="listitem"> | |
| <p class="simpara">The index enables fast comparisons between the tree object it defines | |
| and the working tree.</p> | |
| <p class="simpara">It does this by storing some additional data for each entry (such as | |
| the last modified time). This data is not displayed above, and is not | |
| stored in the created tree object, but it can be used to determine | |
| quickly which files in the working directory differ from what was | |
| stored in the index, and thus save Git from having to read all of the | |
| data from such files to look for changes.</p> | |
| </li><li class="listitem"> | |
| <p class="simpara">It can efficiently represent information about merge conflicts | |
| between different tree objects, allowing each pathname to be | |
| associated with sufficient information about the trees involved that | |
| you can create a three-way merge between them.</p> | |
| <p class="simpara">We saw in <a class="xref" href="#conflict-resolution" title="Getting conflict-resolution help during a merge">the section called “Getting conflict-resolution help during a merge”</a> that during a merge the index can | |
| store multiple versions of a single file (called "stages"). The third | |
| column in the <a class="ulink" href="git-ls-files.html" target="_top">git-ls-files(1)</a> output above is the stage | |
| number, and will take on values other than 0 for files with merge | |
| conflicts.</p> | |
| </li></ol></div> | |
| <p>The index is thus a sort of temporary staging area, which is filled with | |
| a tree which you are in the process of working on.</p> | |
| <p>If you blow the index away entirely, you generally haven’t lost any | |
| information as long as you have the name of the tree that it described.</p> | |
| </div> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="submodules"></a>Chapter 8. Submodules</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#pitfalls-with-submodules">Pitfalls with submodules</a></span></dt></dl></div> | |
| <p>Large projects are often composed of smaller, self-contained modules. For | |
| example, an embedded Linux distribution’s source tree would include every | |
| piece of software in the distribution with some local modifications; a movie | |
| player might need to build against a specific, known-working version of a | |
| decompression library; several independent programs might all share the same | |
| build scripts.</p> | |
| <p>With centralized revision control systems this is often accomplished by | |
| including every module in one single repository. Developers can check out | |
| all modules or only the modules they need to work with. They can even modify | |
| files across several modules in a single commit while moving things around | |
| or updating APIs and translations.</p> | |
| <p>Git does not allow partial checkouts, so duplicating this approach in Git | |
| would force developers to keep a local copy of modules they are not | |
| interested in touching. Commits in an enormous checkout would be slower | |
| than you’d expect as Git would have to scan every directory for changes. | |
| If modules have a lot of local history, clones would take forever.</p> | |
| <p>On the plus side, distributed revision control systems can much better | |
| integrate with external sources. In a centralized model, a single arbitrary | |
| snapshot of the external project is exported from its own revision control | |
| and then imported into the local revision control on a vendor branch. All | |
| the history is hidden. With distributed revision control you can clone the | |
| entire external history and much more easily follow development and re-merge | |
| local changes.</p> | |
| <p>Git’s submodule support allows a repository to contain, as a subdirectory, a | |
| checkout of an external project. Submodules maintain their own identity; | |
| the submodule support just stores the submodule repository location and | |
| commit ID, so other developers who clone the containing project | |
| ("superproject") can easily clone all the submodules at the same revision. | |
| Partial checkouts of the superproject are possible: you can tell Git to | |
| clone none, some or all of the submodules.</p> | |
| <p>The <a class="ulink" href="git-submodule.html" target="_top">git-submodule(1)</a> command is available since Git 1.5.3. Users | |
| with Git 1.5.2 can look up the submodule commits in the repository and | |
| manually check them out; earlier versions won’t recognize the submodules at | |
| all.</p> | |
| <p>To see how submodule support works, create four example | |
| repositories that can be used later as a submodule:</p> | |
| <pre class="screen">$ mkdir ~/git | |
| $ cd ~/git | |
| $ for i in a b c d | |
| do | |
| mkdir $i | |
| cd $i | |
| git init | |
| echo "module $i" > $i.txt | |
| git add $i.txt | |
| git commit -m "Initial commit, submodule $i" | |
| cd .. | |
| done</pre> | |
| <p>Now create the superproject and add all the submodules:</p> | |
| <pre class="screen">$ mkdir super | |
| $ cd super | |
| $ git init | |
| $ for i in a b c d | |
| do | |
| git submodule add ~/git/$i $i | |
| done</pre> | |
| <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3> | |
| <p>Do not use local URLs here if you plan to publish your superproject!</p> | |
| </div> | |
| <p>See what files <code class="literal">git</code> <code class="literal">submodule</code> created:</p> | |
| <pre class="screen">$ ls -a | |
| . .. .git .gitmodules a b c d</pre> | |
| <p>The <code class="literal">git</code> <code class="literal">submodule</code> <code class="literal">add</code> <span class="emphasis"><em><repo></em></span> <span class="emphasis"><em><path></em></span> command does a couple of things:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| It clones the submodule from <span class="emphasis"><em><repo></em></span> to the given <span class="emphasis"><em><path></em></span> under the | |
| current directory and by default checks out the master branch. | |
| </li><li class="listitem"> | |
| It adds the submodule’s clone path to the <a class="ulink" href="gitmodules.html" target="_top">gitmodules(5)</a> file and | |
| adds this file to the index, ready to be committed. | |
| </li><li class="listitem"> | |
| It adds the submodule’s current commit ID to the index, ready to be | |
| committed. | |
| </li></ul></div> | |
| <p>Commit the superproject:</p> | |
| <pre class="screen">$ git commit -m "Add submodules a, b, c and d."</pre> | |
| <p>Now clone the superproject:</p> | |
| <pre class="screen">$ cd .. | |
| $ git clone super cloned | |
| $ cd cloned</pre> | |
| <p>The submodule directories are there, but they’re empty:</p> | |
| <pre class="screen">$ ls -a a | |
| . .. | |
| $ git submodule status | |
| -d266b9873ad50488163457f025db7cdd9683d88b a | |
| -e81d457da15309b4fef4249aba9b50187999670d b | |
| -c1536a972b9affea0f16e0680ba87332dc059146 c | |
| -d96249ff5d57de5de093e6baff9e0aafa5276a74 d</pre> | |
| <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3> | |
| <p>The commit object names shown above would be different for you, but they | |
| should match the HEAD commit object names of your repositories. You can check | |
| it by running <code class="literal">git</code> <code class="literal">ls-remote</code> <code class="literal">..</code><code class="literal">/a</code>.</p> | |
| </div> | |
| <p>Pulling down the submodules is a two-step process. First run <code class="literal">git</code> <code class="literal">submodule</code> | |
| <code class="literal">init</code> to add the submodule repository URLs to .<code class="literal">git/config</code>:</p> | |
| <pre class="screen">$ git submodule init</pre> | |
| <p>Now use <code class="literal">git</code> <code class="literal">submodule</code> <code class="literal">update</code> to clone the repositories and check out the | |
| commits specified in the superproject:</p> | |
| <pre class="screen">$ git submodule update | |
| $ cd a | |
| $ ls -a | |
| . .. .git a.txt</pre> | |
| <p>One major difference between <code class="literal">git</code> <code class="literal">submodule</code> <code class="literal">update</code> and <code class="literal">git</code> <code class="literal">submodule</code> <code class="literal">add</code> is | |
| that <code class="literal">git</code> <code class="literal">submodule</code> <code class="literal">update</code> checks out a specific commit, rather than the tip | |
| of a branch. It’s like checking out a tag: the head is detached, so you’re not | |
| working on a branch.</p> | |
| <pre class="screen">$ git branch | |
| * (detached from d266b98) | |
| master</pre> | |
| <p>If you want to make a change within a submodule and you have a detached head, | |
| then you should create or checkout a branch, make your changes, publish the | |
| change within the submodule, and then update the superproject to reference the | |
| new commit:</p> | |
| <pre class="screen">$ git switch master</pre> | |
| <p>or</p> | |
| <pre class="screen">$ git switch -c fix-up</pre> | |
| <p>then</p> | |
| <pre class="screen">$ echo "adding a line again" >> a.txt | |
| $ git commit -a -m "Updated the submodule from within the superproject." | |
| $ git push | |
| $ cd .. | |
| $ git diff | |
| diff --git a/a b/a | |
| index d266b98..261dfac 160000 | |
| --- a/a | |
| +++ b/a | |
| @@ -1 +1 @@ | |
| -Subproject commit d266b9873ad50488163457f025db7cdd9683d88b | |
| +Subproject commit 261dfac35cb99d380eb966e102c1197139f7fa24 | |
| $ git add a | |
| $ git commit -m "Updated submodule a." | |
| $ git push</pre> | |
| <p>You have to run <code class="literal">git</code> <code class="literal">submodule</code> <code class="literal">update</code> after <code class="literal">git</code> <code class="literal">pull</code> if you want to update | |
| submodules, too.</p> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="pitfalls-with-submodules"></a>Pitfalls with submodules</h2></div></div></div> | |
| <p>Always publish the submodule change before publishing the change to the | |
| superproject that references it. If you forget to publish the submodule change, | |
| others won’t be able to clone the repository:</p> | |
| <pre class="screen">$ cd ~/git/super/a | |
| $ echo i added another line to this file >> a.txt | |
| $ git commit -a -m "doing it wrong this time" | |
| $ cd .. | |
| $ git add a | |
| $ git commit -m "Updated submodule a again." | |
| $ git push | |
| $ cd ~/git/cloned | |
| $ git pull | |
| $ git submodule update | |
| error: pathspec '261dfac35cb99d380eb966e102c1197139f7fa24' did not match any file(s) known to git. | |
| Did you forget to 'git add'? | |
| Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a'</pre> | |
| <p>In older Git versions it could be easily forgotten to commit new or modified | |
| files in a submodule, which silently leads to similar problems as not pushing | |
| the submodule changes. Starting with Git 1.7.0 both <code class="literal">git</code> <code class="literal">status</code> and <code class="literal">git</code> <code class="literal">diff</code> | |
| in the superproject show submodules as modified when they contain new or | |
| modified files to protect against accidentally committing such a state. <code class="literal">git</code> | |
| <code class="literal">diff</code> will also add a <code class="literal">-dirty</code> to the work tree side when generating patch | |
| output or used with the <code class="literal">--submodule</code> option:</p> | |
| <pre class="screen">$ git diff | |
| diff --git a/sub b/sub | |
| --- a/sub | |
| +++ b/sub | |
| @@ -1 +1 @@ | |
| -Subproject commit 3f356705649b5d566d97ff843cf193359229a453 | |
| +Subproject commit 3f356705649b5d566d97ff843cf193359229a453-dirty | |
| $ git diff --submodule | |
| Submodule sub 3f35670..3f35670-dirty:</pre> | |
| <p>You also should not rewind branches in a submodule beyond commits that were | |
| ever recorded in any superproject.</p> | |
| <p>It’s not safe to run <code class="literal">git</code> <code class="literal">submodule</code> <code class="literal">update</code> if you’ve made and committed | |
| changes within a submodule without checking out a branch first. They will be | |
| silently overwritten:</p> | |
| <pre class="screen">$ cat a.txt | |
| module a | |
| $ echo line added from private2 >> a.txt | |
| $ git commit -a -m "line added inside private2" | |
| $ cd .. | |
| $ git submodule update | |
| Submodule path 'a': checked out 'd266b9873ad50488163457f025db7cdd9683d88b' | |
| $ cd a | |
| $ cat a.txt | |
| module a</pre> | |
| <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3> | |
| <p>The changes are still visible in the submodule’s reflog.</p> | |
| </div> | |
| <p>If you have uncommitted changes in your submodule working tree, <code class="literal">git</code> | |
| <code class="literal">submodule</code> <code class="literal">update</code> will not overwrite them. Instead, you get the usual | |
| warning about not being able switch from a dirty branch.</p> | |
| </div> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="low-level-operations"></a>Chapter 9. Low-level Git operations</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#object-manipulation">Object access and manipulation</a></span></dt><dt><span class="section"><a href="#the-workflow">The Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#working-directory-to-index">working directory → index</a></span></dt><dt><span class="section"><a href="#index-to-object-database">index → object database</a></span></dt><dt><span class="section"><a href="#object-database-to-index">object database → index</a></span></dt><dt><span class="section"><a href="#index-to-working-directory">index → working directory</a></span></dt><dt><span class="section"><a href="#tying-it-all-together">Tying it all together</a></span></dt></dl></dd><dt><span class="section"><a href="#examining-the-data">Examining the data</a></span></dt><dt><span class="section"><a href="#merging-multiple-trees">Merging multiple trees</a></span></dt><dt><span class="section"><a href="#merging-multiple-trees-2">Merging multiple trees, continued</a></span></dt></dl></div> | |
| <p>Many of the higher-level commands were originally implemented as shell | |
| scripts using a smaller core of low-level Git commands. These can still | |
| be useful when doing unusual things with Git, or just as a way to | |
| understand its inner workings.</p> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="object-manipulation"></a>Object access and manipulation</h2></div></div></div> | |
| <p>The <a class="ulink" href="git-cat-file.html" target="_top">git-cat-file(1)</a> command can show the contents of any object, | |
| though the higher-level <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> is usually more useful.</p> | |
| <p>The <a class="ulink" href="git-commit-tree.html" target="_top">git-commit-tree(1)</a> command allows constructing commits with | |
| arbitrary parents and trees.</p> | |
| <p>A tree can be created with <a class="ulink" href="git-write-tree.html" target="_top">git-write-tree(1)</a> and its data can be | |
| accessed by <a class="ulink" href="git-ls-tree.html" target="_top">git-ls-tree(1)</a>. Two trees can be compared with | |
| <a class="ulink" href="git-diff-tree.html" target="_top">git-diff-tree(1)</a>.</p> | |
| <p>A tag is created with <a class="ulink" href="git-mktag.html" target="_top">git-mktag(1)</a>, and the signature can be | |
| verified by <a class="ulink" href="git-verify-tag.html" target="_top">git-verify-tag(1)</a>, though it is normally simpler to | |
| use <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> for both.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="the-workflow"></a>The Workflow</h2></div></div></div> | |
| <p>High-level operations such as <a class="ulink" href="git-commit.html" target="_top">git-commit(1)</a> and | |
| <a class="ulink" href="git-restore.html" target="_top">git-restore(1)</a> work by moving data | |
| between the working tree, the index, and the object database. Git | |
| provides low-level operations which perform each of these steps | |
| individually.</p> | |
| <p>Generally, all Git operations work on the index file. Some operations | |
| work <span class="strong"><strong>purely</strong></span> on the index file (showing the current state of the | |
| index), but most operations move data between the index file and either | |
| the database or the working directory. Thus there are four main | |
| combinations:</p> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="working-directory-to-index"></a>working directory → index</h3></div></div></div> | |
| <p>The <a class="ulink" href="git-update-index.html" target="_top">git-update-index(1)</a> command updates the index with | |
| information from the working directory. You generally update the | |
| index information by just specifying the filename you want to update, | |
| like so:</p> | |
| <pre class="screen">$ git update-index filename</pre> | |
| <p>but to avoid common mistakes with filename globbing etc., the command | |
| will not normally add totally new entries or remove old entries, | |
| i.e. it will normally just update existing cache entries.</p> | |
| <p>To tell Git that yes, you really do realize that certain files no | |
| longer exist, or that new files should be added, you | |
| should use the <code class="literal">--remove</code> and <code class="literal">--add</code> flags respectively.</p> | |
| <p>NOTE! A <code class="literal">--remove</code> flag does <span class="emphasis"><em>not</em></span> mean that subsequent filenames will | |
| necessarily be removed: if the files still exist in your directory | |
| structure, the index will be updated with their new status, not | |
| removed. The only thing <code class="literal">--remove</code> means is that update-index will be | |
| considering a removed file to be a valid thing, and if the file really | |
| does not exist any more, it will update the index accordingly.</p> | |
| <p>As a special case, you can also do <code class="literal">git</code> <code class="literal">update-index</code> <code class="literal">--refresh</code>, which | |
| will refresh the "stat" information of each index to match the current | |
| stat information. It will <span class="emphasis"><em>not</em></span> update the object status itself, and | |
| it will only update the fields that are used to quickly test whether | |
| an object still matches its old backing store object.</p> | |
| <p>The previously introduced <a class="ulink" href="git-add.html" target="_top">git-add(1)</a> is just a wrapper for | |
| <a class="ulink" href="git-update-index.html" target="_top">git-update-index(1)</a>.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="index-to-object-database"></a>index → object database</h3></div></div></div> | |
| <p>You write your current index file to a "tree" object with the program</p> | |
| <pre class="screen">$ git write-tree</pre> | |
| <p>that doesn’t come with any options—it will just write out the | |
| current index into the set of tree objects that describe that state, | |
| and it will return the name of the resulting top-level tree. You can | |
| use that tree to re-generate the index at any time by going in the | |
| other direction:</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="object-database-to-index"></a>object database → index</h3></div></div></div> | |
| <p>You read a "tree" file from the object database, and use that to | |
| populate (and overwrite—don’t do this if your index contains any | |
| unsaved state that you might want to restore later!) your current | |
| index. Normal operation is just</p> | |
| <pre class="screen">$ git read-tree <SHA-1 of tree></pre> | |
| <p>and your index file will now be equivalent to the tree that you saved | |
| earlier. However, that is only your <span class="emphasis"><em>index</em></span> file: your working | |
| directory contents have not been modified.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="index-to-working-directory"></a>index → working directory</h3></div></div></div> | |
| <p>You update your working directory from the index by "checking out" | |
| files. This is not a very common operation, since normally you’d just | |
| keep your files updated, and rather than write to your working | |
| directory, you’d tell the index files about the changes in your | |
| working directory (i.e. <code class="literal">git</code> <code class="literal">update-index</code>).</p> | |
| <p>However, if you decide to jump to a new version, or check out somebody | |
| else’s version, or just restore a previous tree, you’d populate your | |
| index file with read-tree, and then you need to check out the result | |
| with</p> | |
| <pre class="screen">$ git checkout-index filename</pre> | |
| <p>or, if you want to check out all of the index, use <code class="literal">-a</code>.</p> | |
| <p>NOTE! <code class="literal">git</code> <code class="literal">checkout-index</code> normally refuses to overwrite old files, so | |
| if you have an old version of the tree already checked out, you will | |
| need to use the <code class="literal">-f</code> flag (<span class="emphasis"><em>before</em></span> the <code class="literal">-a</code> flag or the filename) to | |
| <span class="emphasis"><em>force</em></span> the checkout.</p> | |
| <p>Finally, there are a few odds and ends which are not purely moving | |
| from one representation to the other:</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="tying-it-all-together"></a>Tying it all together</h3></div></div></div> | |
| <p>To commit a tree you have instantiated with <code class="literal">git</code> <code class="literal">write-tree</code>, you’d | |
| create a "commit" object that refers to that tree and the history | |
| behind it—most notably the "parent" commits that preceded it in | |
| history.</p> | |
| <p>Normally a "commit" has one parent: the previous state of the tree | |
| before a certain change was made. However, sometimes it can have two | |
| or more parent commits, in which case we call it a "merge", due to the | |
| fact that such a commit brings together ("merges") two or more | |
| previous states represented by other commits.</p> | |
| <p>In other words, while a "tree" represents a particular directory state | |
| of a working directory, a "commit" represents that state in time, | |
| and explains how we got there.</p> | |
| <p>You create a commit object by giving it the tree that describes the | |
| state at the time of the commit, and a list of parents:</p> | |
| <pre class="screen">$ git commit-tree <tree> -p <parent> [(-p <parent2>)...]</pre> | |
| <p>and then giving the reason for the commit on stdin (either through | |
| redirection from a pipe or file, or by just typing it at the tty).</p> | |
| <p><code class="literal">git</code> <code class="literal">commit-tree</code> will return the name of the object that represents | |
| that commit, and you should save it away for later use. Normally, | |
| you’d commit a new <code class="literal">HEAD</code> state, and while Git doesn’t care where you | |
| save the note about that state, in practice we tend to just write the | |
| result to the file pointed at by .<code class="literal">git/HEAD</code>, so that we can always see | |
| what the last committed state was.</p> | |
| <p>Here is a picture that illustrates how various pieces fit together:</p> | |
| <pre class="screen"> commit-tree | |
| commit obj | |
| +----+ | |
| | | | |
| | | | |
| V V | |
| +-----------+ | |
| | Object DB | | |
| | Backing | | |
| | Store | | |
| +-----------+ | |
| ^ | |
| write-tree | | | |
| tree obj | | | |
| | | read-tree | |
| | | tree obj | |
| V | |
| +-----------+ | |
| | Index | | |
| | "cache" | | |
| +-----------+ | |
| update-index ^ | |
| blob obj | | | |
| | | | |
| checkout-index -u | | checkout-index | |
| stat | | blob obj | |
| V | |
| +-----------+ | |
| | Working | | |
| | Directory | | |
| +-----------+</pre> | |
| </div> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="examining-the-data"></a>Examining the data</h2></div></div></div> | |
| <p>You can examine the data represented in the object database and the | |
| index with various helper tools. For every object, you can use | |
| <a class="ulink" href="git-cat-file.html" target="_top">git-cat-file(1)</a> to examine details about the | |
| object:</p> | |
| <pre class="screen">$ git cat-file -t <objectname></pre> | |
| <p>shows the type of the object, and once you have the type (which is | |
| usually implicit in where you find the object), you can use</p> | |
| <pre class="screen">$ git cat-file blob|tree|commit|tag <objectname></pre> | |
| <p>to show its contents. NOTE! Trees have binary content, and as a result | |
| there is a special helper for showing that content, called | |
| <code class="literal">git</code> <code class="literal">ls-tree</code>, which turns the binary content into a more easily | |
| readable form.</p> | |
| <p>It’s especially instructive to look at "commit" objects, since those | |
| tend to be small and fairly self-explanatory. In particular, if you | |
| follow the convention of having the top commit name in .<code class="literal">git/HEAD</code>, | |
| you can do</p> | |
| <pre class="screen">$ git cat-file commit HEAD</pre> | |
| <p>to see what the top commit was.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="merging-multiple-trees"></a>Merging multiple trees</h2></div></div></div> | |
| <p>Git can help you perform a three-way merge, which can in turn be | |
| used for a many-way merge by repeating the merge procedure several | |
| times. The usual situation is that you only do one three-way merge | |
| (reconciling two lines of history) and commit the result, but if | |
| you like to, you can merge several branches in one go.</p> | |
| <p>To perform a three-way merge, you start with the two commits you | |
| want to merge, find their closest common parent (a third commit), | |
| and compare the trees corresponding to these three commits.</p> | |
| <p>To get the "base" for the merge, look up the common parent of two | |
| commits:</p> | |
| <pre class="screen">$ git merge-base <commit1> <commit2></pre> | |
| <p>This prints the name of a commit they are both based on. You should | |
| now look up the tree objects of those commits, which you can easily | |
| do with</p> | |
| <pre class="screen">$ git cat-file commit <commitname> | head -1</pre> | |
| <p>since the tree object information is always the first line in a commit | |
| object.</p> | |
| <p>Once you know the three trees you are going to merge (the one "original" | |
| tree, aka the common tree, and the two "result" trees, aka the branches | |
| you want to merge), you do a "merge" read into the index. This will | |
| complain if it has to throw away your old index contents, so you should | |
| make sure that you’ve committed those—in fact you would normally | |
| always do a merge against your last commit (which should thus match what | |
| you have in your current index anyway).</p> | |
| <p>To do the merge, do</p> | |
| <pre class="screen">$ git read-tree -m -u <origtree> <yourtree> <targettree></pre> | |
| <p>which will do all trivial merge operations for you directly in the | |
| index file, and you can just write the result out with | |
| <code class="literal">git</code> <code class="literal">write-tree</code>.</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="merging-multiple-trees-2"></a>Merging multiple trees, continued</h2></div></div></div> | |
| <p>Sadly, many merges aren’t trivial. If there are files that have | |
| been added, moved or removed, or if both branches have modified the | |
| same file, you will be left with an index tree that contains "merge | |
| entries" in it. Such an index tree can <span class="emphasis"><em>NOT</em></span> be written out to a tree | |
| object, and you will have to resolve any such merge clashes using | |
| other tools before you can write out the result.</p> | |
| <p>You can examine such index state with <code class="literal">git</code> <code class="literal">ls-files</code> <code class="literal">--unmerged</code> | |
| command. An example:</p> | |
| <pre class="screen">$ git read-tree -m $orig HEAD $target | |
| $ git ls-files --unmerged | |
| 100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c | |
| 100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c | |
| 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c</pre> | |
| <p>Each line of the <code class="literal">git</code> <code class="literal">ls-files</code> <code class="literal">--unmerged</code> output begins with | |
| the blob mode bits, blob SHA-1, <span class="emphasis"><em>stage number</em></span>, and the | |
| filename. The <span class="emphasis"><em>stage number</em></span> is Git’s way to say which tree it | |
| came from: stage 1 corresponds to the <code class="literal">$orig</code> tree, stage 2 to | |
| the <code class="literal">HEAD</code> tree, and stage 3 to the <code class="literal">$target</code> tree.</p> | |
| <p>Earlier we said that trivial merges are done inside | |
| <code class="literal">git</code> <code class="literal">read-tree</code> <code class="literal">-m</code>. For example, if the file did not change | |
| from <code class="literal">$orig</code> to <code class="literal">HEAD</code> or <code class="literal">$target</code>, or if the file changed | |
| from <code class="literal">$orig</code> to <code class="literal">HEAD</code> and <code class="literal">$orig</code> to <code class="literal">$target</code> the same way, | |
| obviously the final outcome is what is in <code class="literal">HEAD</code>. What the | |
| above example shows is that file <code class="literal">hello.c</code> was changed from | |
| <code class="literal">$orig</code> to <code class="literal">HEAD</code> and <code class="literal">$orig</code> to <code class="literal">$target</code> in a different way. | |
| You could resolve this by running your favorite 3-way merge | |
| program, e.g. <code class="literal">diff3</code>, <code class="literal">merge</code>, or Git’s own merge-file, on | |
| the blob objects from these three stages yourself, like this:</p> | |
| <pre class="screen">$ git cat-file blob 263414f >hello.c~1 | |
| $ git cat-file blob 06fa6a2 >hello.c~2 | |
| $ git cat-file blob cc44c73 >hello.c~3 | |
| $ git merge-file hello.c~2 hello.c~1 hello.c~3</pre> | |
| <p>This would leave the merge result in <code class="literal">hello.c~2</code> file, along | |
| with conflict markers if there are conflicts. After verifying | |
| the merge result makes sense, you can tell Git what the final | |
| merge result for this file is by:</p> | |
| <pre class="screen">$ mv -f hello.c~2 hello.c | |
| $ git update-index hello.c</pre> | |
| <p>When a path is in the "unmerged" state, running <code class="literal">git</code> <code class="literal">update-index</code> for | |
| that path tells Git to mark the path resolved.</p> | |
| <p>The above is the description of a Git merge at the lowest level, | |
| to help you understand what conceptually happens under the hood. | |
| In practice, nobody, not even Git itself, runs <code class="literal">git</code> <code class="literal">cat-file</code> three times | |
| for this. There is a <code class="literal">git</code> <code class="literal">merge-index</code> program that extracts the | |
| stages to temporary files and calls a "merge" script on it:</p> | |
| <pre class="screen">$ git merge-index git-merge-one-file hello.c</pre> | |
| <p>and that is what higher level <code class="literal">git</code> <code class="literal">merge</code> <code class="literal">-s</code> <code class="literal">resolve</code> is implemented with.</p> | |
| </div> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="hacking-git"></a>Chapter 10. Hacking Git</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#object-details">Object storage format</a></span></dt><dt><span class="section"><a href="#birdview-on-the-source-code">A birds-eye view of Git’s source code</a></span></dt></dl></div> | |
| <p>This chapter covers internal details of the Git implementation which | |
| probably only Git developers need to understand.</p> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="object-details"></a>Object storage format</h2></div></div></div> | |
| <p>All objects have a statically determined "type" which identifies the | |
| format of the object (i.e. how it is used, and how it can refer to other | |
| objects). There are currently four different object types: "blob", | |
| "tree", "commit", and "tag".</p> | |
| <p>Regardless of object type, all objects share the following | |
| characteristics: they are all deflated with zlib, and have a header | |
| that not only specifies their type, but also provides size information | |
| about the data in the object. It’s worth noting that the SHA-1 hash | |
| that is used to name the object is the hash of the original data | |
| plus this header, so <code class="literal">sha1sum</code> <span class="emphasis"><em>file</em></span> does not match the object name | |
| for <span class="emphasis"><em>file</em></span> (the earliest versions of Git hashed slightly differently | |
| but the conclusion is still the same).</p> | |
| <p>The following is a short example that demonstrates how these hashes | |
| can be generated manually:</p> | |
| <p>Let’s assume a small text file with some simple content:</p> | |
| <pre class="screen">$ echo "Hello world" >hello.txt</pre> | |
| <p>We can now manually generate the hash Git would use for this file:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| The object we want the hash for is of type "blob" and its size is | |
| 12 bytes. | |
| </li><li class="listitem"> | |
| Prepend the object header to the file content and feed this to | |
| <code class="literal">sha1sum</code>: | |
| </li></ul></div> | |
| <pre class="screen">$ { printf "blob 12\0"; cat hello.txt; } | sha1sum | |
| 802992c4220de19a90767f3000a79a31b98d0df7 -</pre> | |
| <p>This manually constructed hash can be verified using <code class="literal">git</code> <code class="literal">hash-object</code> | |
| which of course hides the addition of the header:</p> | |
| <pre class="screen">$ git hash-object hello.txt | |
| 802992c4220de19a90767f3000a79a31b98d0df7</pre> | |
| <p>As a result, the general consistency of an object can always be tested | |
| independently of the contents or the type of the object: all objects can | |
| be validated by verifying that (a) their hashes match the content of the | |
| file and (b) the object successfully inflates to a stream of bytes that | |
| forms a sequence of | |
| <span class="emphasis"><em><ascii-type-without-space></em></span> <code class="literal">+</code> <span class="emphasis"><em><space></em></span> <code class="literal">+</code> <span class="emphasis"><em><ascii-decimal-size></em></span> <code class="literal">+</code> | |
| <byte\0> <code class="literal">+</code> <span class="emphasis"><em><binary-object-data></em></span>.</p> | |
| <p>The structured objects can further have their structure and | |
| connectivity to other objects verified. This is generally done with | |
| the <code class="literal">git</code> <code class="literal">fsck</code> program, which generates a full dependency graph | |
| of all objects, and verifies their internal consistency (in addition | |
| to just verifying their superficial consistency through the hash).</p> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="birdview-on-the-source-code"></a>A birds-eye view of Git’s source code</h2></div></div></div> | |
| <p>It is not always easy for new developers to find their way through Git’s | |
| source code. This section gives you a little guidance to show where to | |
| start.</p> | |
| <p>A good place to start is with the contents of the initial commit, with:</p> | |
| <pre class="screen">$ git switch --detach e83c5163</pre> | |
| <p>The initial revision lays the foundation for almost everything Git has | |
| today (even though details may differ in a few places), but is small | |
| enough to read in one sitting.</p> | |
| <p>Note that terminology has changed since that revision. For example, the | |
| README in that revision uses the word "changeset" to describe what we | |
| now call a <a class="link" href="#def_commit_object">commit</a>.</p> | |
| <p>Also, we do not call it "cache" any more, but rather "index"; however, | |
| the file is still called <code class="literal">read-cache.h</code>.</p> | |
| <p>If you grasp the ideas in that initial commit, you should check out a | |
| more recent version and skim <code class="literal">read-cache-ll.h</code>, <code class="literal">object.h</code> and <code class="literal">commit.h</code>.</p> | |
| <p>In the early days, Git (in the tradition of UNIX) was a bunch of programs | |
| which were extremely simple, and which you used in scripts, piping the | |
| output of one into another. This turned out to be good for initial | |
| development, since it was easier to test new things. However, recently | |
| many of these parts have become builtins, and some of the core has been | |
| "libified", i.e. put into libgit.a for performance, portability reasons, | |
| and to avoid code duplication.</p> | |
| <p>By now, you know what the index is (and find the corresponding data | |
| structures in <code class="literal">read-cache-ll.h</code>), and that there are just a couple of | |
| object types (blobs, trees, commits and tags) which inherit their | |
| common structure from <code class="literal">struct</code> <code class="literal">object</code>, which is their first member | |
| (and thus, you can cast e.g. (<code class="literal">struct</code> <code class="literal">object</code> <code class="literal">*</code>)<code class="literal">commit</code> to achieve the | |
| <span class="emphasis"><em>same</em></span> as &commit-><code class="literal">object</code>, i.e. get at the object name and flags).</p> | |
| <p>Now is a good point to take a break to let this information sink in.</p> | |
| <p>Next step: get familiar with the object naming. Read <a class="xref" href="#naming-commits" title="Naming commits">the section called “Naming commits”</a>. | |
| There are quite a few ways to name an object (and not only revisions!). | |
| All of these are handled in <code class="literal">sha1_name.c</code>. Just have a quick look at | |
| the function <code class="literal">get_sha1</code>(). A lot of the special handling is done by | |
| functions like <code class="literal">get_sha1_basic</code>() or the likes.</p> | |
| <p>This is just to get you into the groove for the most libified part of Git: | |
| the revision walker.</p> | |
| <p>Basically, the initial version of <code class="literal">git</code> <code class="literal">log</code> was a shell script:</p> | |
| <pre class="screen">$ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \ | |
| LESS=-S ${PAGER:-less}</pre> | |
| <p>What does this mean?</p> | |
| <p><code class="literal">git</code> <code class="literal">rev-list</code> is the original version of the revision walker, which | |
| <span class="emphasis"><em>always</em></span> printed a list of revisions to stdout. It is still functional, | |
| and needs to, since most new Git commands start out as scripts using | |
| <code class="literal">git</code> <code class="literal">rev-list</code>.</p> | |
| <p><code class="literal">git</code> <code class="literal">rev-parse</code> is not as important any more; it was only used to filter out | |
| options that were relevant for the different plumbing commands that were | |
| called by the script.</p> | |
| <p>Most of what <code class="literal">git</code> <code class="literal">rev-list</code> did is contained in <code class="literal">revision.c</code> and | |
| <code class="literal">revision.h</code>. It wraps the options in a struct named <code class="literal">rev_info</code>, which | |
| controls how and what revisions are walked, and more.</p> | |
| <p>The original job of <code class="literal">git</code> <code class="literal">rev-parse</code> is now taken by the function | |
| <code class="literal">setup_revisions</code>(), which parses the revisions and the common command-line | |
| options for the revision walker. This information is stored in the struct | |
| <code class="literal">rev_info</code> for later consumption. You can do your own command-line option | |
| parsing after calling <code class="literal">setup_revisions</code>(). After that, you have to call | |
| <code class="literal">prepare_revision_walk</code>() for initialization, and then you can get the | |
| commits one by one with the function <code class="literal">get_revision</code>().</p> | |
| <p>If you are interested in more details of the revision walking process, | |
| just have a look at the first implementation of <code class="literal">cmd_log</code>(); call | |
| <code class="literal">git</code> <code class="literal">show</code> <code class="literal">v1.3.0~155^2~4</code> and scroll down to that function (note that you | |
| no longer need to call <code class="literal">setup_pager</code>() directly).</p> | |
| <p>Nowadays, <code class="literal">git</code> <code class="literal">log</code> is a builtin, which means that it is <span class="emphasis"><em>contained</em></span> in the | |
| command <code class="literal">git</code>. The source side of a builtin is</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| a function called <code class="literal">cmd_</code><span class="emphasis"><em><bla></em></span>, typically defined in <code class="literal">builtin/</code><bla.<code class="literal">c</code>> | |
| (note that older versions of Git used to have it in <code class="literal">builtin-</code><span class="emphasis"><em><bla></em></span><code class="literal">.c</code> | |
| instead), and declared in <code class="literal">builtin.h</code>. | |
| </li><li class="listitem"> | |
| an entry in the <code class="literal">commands</code>[] array in <code class="literal">git.c</code>, and | |
| </li><li class="listitem"> | |
| an entry in <code class="literal">BUILTIN_OBJECTS</code> in the <code class="literal">Makefile</code>. | |
| </li></ul></div> | |
| <p>Sometimes, more than one builtin is contained in one source file. For | |
| example, <code class="literal">cmd_show</code>() and <code class="literal">cmd_log</code>() both reside in <code class="literal">builtin/log.c</code>, | |
| since they share quite a bit of code. In that case, the commands which are | |
| <span class="emphasis"><em>not</em></span> named like the .<code class="literal">c</code> file in which they live have to be listed in | |
| <code class="literal">BUILT_INS</code> in the <code class="literal">Makefile</code>.</p> | |
| <p><code class="literal">git</code> <code class="literal">log</code> looks more complicated in C than it does in the original script, | |
| but that allows for a much greater flexibility and performance.</p> | |
| <p>Here again it is a good point to take a pause.</p> | |
| <p>Lesson three is: study the code. Really, it is the best way to learn about | |
| the organization of Git (after you know the basic concepts).</p> | |
| <p>So, think about something which you are interested in, say, "how can I | |
| access a blob just knowing the object name of it?". The first step is to | |
| find a Git command with which you can do it. In this example, it is either | |
| <code class="literal">git</code> <code class="literal">show</code> or <code class="literal">git</code> <code class="literal">cat-file</code>.</p> | |
| <p>For the sake of clarity, let’s stay with <code class="literal">git</code> <code class="literal">cat-file</code>, because it</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| is plumbing, and | |
| </li><li class="listitem"> | |
| was around even in the initial commit (it literally went only through | |
| some 20 revisions as <code class="literal">cat-file.c</code>, was renamed to <code class="literal">builtin/cat-file.c</code> | |
| when made a builtin, and then saw less than 10 versions). | |
| </li></ul></div> | |
| <p>So, look into <code class="literal">builtin/cat-file.c</code>, search for <code class="literal">cmd_cat_file</code>() and look what | |
| it does.</p> | |
| <pre class="screen"> repo_config(the_repository, git_default_config); | |
| if (argc != 3) | |
| usage("git cat-file [-t|-s|-e|-p|<type>] <sha1>"); | |
| if (get_sha1(argv[2], sha1)) | |
| die("Not a valid object name %s", argv[2]);</pre> | |
| <p>Let’s skip over the obvious details; the only really interesting part | |
| here is the call to <code class="literal">get_sha1</code>(). It tries to interpret <code class="literal">argv</code>[<code class="literal">2</code>] as an | |
| object name, and if it refers to an object which is present in the current | |
| repository, it writes the resulting SHA-1 into the variable <code class="literal">sha1</code>.</p> | |
| <p>Two things are interesting here:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| <code class="literal">get_sha1</code>() returns 0 on <span class="emphasis"><em>success</em></span>. This might surprise some new | |
| Git hackers, but there is a long tradition in UNIX to return different | |
| negative numbers in case of different errors—and 0 on success. | |
| </li><li class="listitem"> | |
| the variable <code class="literal">sha1</code> in the function signature of <code class="literal">get_sha1</code>() is <code class="literal">unsigned</code> | |
| <code class="literal">char</code> <code class="literal">*</code>, but is actually expected to be a pointer to <code class="literal">unsigned</code> | |
| <code class="literal">char</code>[<code class="literal">20</code>]. This variable will contain the 160-bit SHA-1 of the given | |
| commit. Note that whenever a SHA-1 is passed as <code class="literal">unsigned</code> <code class="literal">char</code> <code class="literal">*</code>, it | |
| is the binary representation, as opposed to the ASCII representation in | |
| hex characters, which is passed as <code class="literal">char</code> <code class="literal">*</code>. | |
| </li></ul></div> | |
| <p>You will see both of these things throughout the code.</p> | |
| <p>Now, for the meat:</p> | |
| <pre class="screen"> case 0: | |
| buf = odb_read_object_peeled(r->objects, sha1, argv[1], &size, NULL);</pre> | |
| <p>This is how you read a blob (actually, not only a blob, but any type of | |
| object). To know how the function <code class="literal">odb_read_object_peeled</code>() actually | |
| works, find the source code for it (something like <code class="literal">git</code> <code class="literal">grep</code> | |
| <code class="literal">read_object_with</code> | <code class="literal">grep</code> ":[<code class="literal">a-z</code>]" in the Git repository), and read | |
| the source.</p> | |
| <p>To find out how the result can be used, just read on in <code class="literal">cmd_cat_file</code>():</p> | |
| <pre class="screen"> write_or_die(1, buf, size);</pre> | |
| <p>Sometimes, you do not know where to look for a feature. In many such cases, | |
| it helps to search through the output of <code class="literal">git</code> <code class="literal">log</code>, and then <code class="literal">git</code> <code class="literal">show</code> the | |
| corresponding commit.</p> | |
| <p>Example: If you know that there was some test case for <code class="literal">git</code> <code class="literal">bundle</code>, but | |
| do not remember where it was (yes, you <span class="emphasis"><em>could</em></span> <code class="literal">git</code> <code class="literal">grep</code> <code class="literal">bundle</code> <code class="literal">t/</code>, but that | |
| does not illustrate the point!):</p> | |
| <pre class="screen">$ git log --no-merges t/</pre> | |
| <p>In the pager (<code class="literal">less</code>), just search for "bundle", go a few lines back, | |
| and see that it is in commit 18449ab0. Now just copy this object name, | |
| and paste it into the command line</p> | |
| <pre class="screen">$ git show 18449ab0</pre> | |
| <p>Voila.</p> | |
| <p>Another example: Find out what to do in order to make some script a | |
| builtin:</p> | |
| <pre class="screen">$ git log --no-merges --diff-filter=A builtin/*.c</pre> | |
| <p>You see, Git is actually the best tool to find out about the source of Git | |
| itself!</p> | |
| </div> | |
| </div> | |
| <div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="glossary"></a>Chapter 11. Git Glossary</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#git-explained">Git explained</a></span></dt></dl></div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="git-explained"></a>Git explained</h2></div></div></div> | |
| <div class="variablelist"><dl class="variablelist"><dt><span class="term"><a name="def_alternate_object_database"></a>alternate object database</span></dt><dd> | |
| Via the alternates mechanism, a <a class="link" href="#def_repository">repository</a> | |
| can inherit part of its <a class="link" href="#def_object_database">object database</a> | |
| from another object database, which is called an "alternate". | |
| </dd><dt><span class="term"><a name="def_bare_repository"></a>bare repository</span></dt><dd> | |
| A bare repository is normally an appropriately | |
| named <a class="link" href="#def_directory">directory</a> with a .<code class="literal">git</code> suffix that does not | |
| have a locally checked-out copy of any of the files under | |
| revision control. That is, all of the Git | |
| administrative and control files that would normally be present in the | |
| hidden .<code class="literal">git</code> sub-directory are directly present in the | |
| <code class="literal">repository.git</code> directory instead, | |
| and no other files are present and checked out. Usually publishers of | |
| public repositories make bare repositories available. | |
| </dd><dt><span class="term"><a name="def_blob_object"></a>blob object</span></dt><dd> | |
| Untyped <a class="link" href="#def_object">object</a>, e.g. the contents of a file. | |
| </dd><dt><span class="term"><a name="def_branch"></a>branch</span></dt><dd> | |
| A "branch" is a line of development. The most recent | |
| <a class="link" href="#def_commit">commit</a> on a branch is referred to as the tip of | |
| that branch. The tip of the branch is <a class="link" href="#def_ref">referenced</a> by a branch | |
| <a class="link" href="#def_head">head</a>, which moves forward as additional development | |
| is done on the branch. A single Git | |
| <a class="link" href="#def_repository">repository</a> can track an arbitrary number of | |
| branches, but your <a class="link" href="#def_working_tree">working tree</a> is | |
| associated with just one of them (the "current" or "checked out" | |
| branch), and <a class="link" href="#def_HEAD">HEAD</a> points to that branch. | |
| </dd><dt><span class="term"><a name="def_cache"></a>cache</span></dt><dd> | |
| Obsolete for: <a class="link" href="#def_index">index</a>. | |
| </dd><dt><span class="term"><a name="def_chain"></a>chain</span></dt><dd> | |
| A list of objects, where each <a class="link" href="#def_object">object</a> in the list contains | |
| a reference to its successor (for example, the successor of a | |
| <a class="link" href="#def_commit">commit</a> could be one of its <a class="link" href="#def_parent">parents</a>). | |
| </dd><dt><span class="term"><a name="def_changeset"></a>changeset</span></dt><dd> | |
| BitKeeper/cvsps speak for "<a class="link" href="#def_commit">commit</a>". Since Git does not | |
| store changes, but states, it really does not make sense to use the term | |
| "changesets" with Git. | |
| </dd><dt><span class="term"><a name="def_checkout"></a>checkout</span></dt><dd> | |
| The action of updating all or part of the | |
| <a class="link" href="#def_working_tree">working tree</a> with a <a class="link" href="#def_tree_object">tree object</a> | |
| or <a class="link" href="#def_blob_object">blob</a> from the | |
| <a class="link" href="#def_object_database">object database</a>, and updating the | |
| <a class="link" href="#def_index">index</a> and <a class="link" href="#def_HEAD">HEAD</a> if the whole working tree has | |
| been pointed at a new <a class="link" href="#def_branch">branch</a>. | |
| </dd><dt><span class="term"><a name="def_cherry-picking"></a>cherry-picking</span></dt><dd> | |
| In <a class="link" href="#def_SCM">SCM</a> jargon, "cherry pick" means to choose a subset of | |
| changes out of a series of changes (typically commits) and record them | |
| as a new series of changes on top of a different codebase. In Git, this is | |
| performed by the "git cherry-pick" command to extract the change introduced | |
| by an existing <a class="link" href="#def_commit">commit</a> and to record it based on the tip | |
| of the current <a class="link" href="#def_branch">branch</a> as a new commit. | |
| </dd><dt><span class="term"><a name="def_clean"></a>clean</span></dt><dd> | |
| A <a class="link" href="#def_working_tree">working tree</a> is clean, if it | |
| corresponds to the <a class="link" href="#def_revision">revision</a> referenced by the current | |
| <a class="link" href="#def_head">head</a>. Also see "<a class="link" href="#def_dirty">dirty</a>". | |
| </dd><dt><span class="term"><a name="def_commit"></a>commit</span></dt><dd> | |
| <p class="simpara">As a noun: A single point in the | |
| Git history; the entire history of a project is represented as a | |
| set of interrelated commits. The word "commit" is often | |
| used by Git in the same places other revision control systems | |
| use the words "revision" or "version". Also used as a short | |
| hand for <a class="link" href="#def_commit_object">commit object</a>.</p> | |
| <p class="simpara">As a verb: The action of storing a new snapshot of the project’s | |
| state in the Git history, by creating a new commit representing the current | |
| state of the <a class="link" href="#def_index">index</a> and advancing <a class="link" href="#def_HEAD">HEAD</a> | |
| to point at the new commit.</p> | |
| </dd><dt><span class="term"><a name="def_commit_graph_general"></a>commit graph concept, representations and usage</span></dt><dd> | |
| A synonym for the <a class="link" href="#def_DAG">DAG</a> structure formed by the commits | |
| in the object database, <a class="link" href="#def_ref">referenced</a> by branch tips, | |
| using their <a class="link" href="#def_chain">chain</a> of linked commits. | |
| This structure is the definitive commit graph. The | |
| graph can be represented in other ways, e.g. the | |
| <a class="link" href="#def_commit_graph_file">"commit-graph" file</a>. | |
| </dd><dt><span class="term"><a name="def_commit_graph_file"></a>commit-graph file</span></dt><dd> | |
| The "commit-graph" (normally hyphenated) file is a supplemental | |
| representation of the <a class="link" href="#def_commit_graph_general">commit graph</a> | |
| which accelerates commit graph walks. The "commit-graph" file is | |
| stored either in the .git/objects/info directory or in the info | |
| directory of an alternate object database. | |
| </dd><dt><span class="term"><a name="def_commit_object"></a>commit object</span></dt><dd> | |
| An <a class="link" href="#def_object">object</a> which contains the information about a | |
| particular <a class="link" href="#def_revision">revision</a>, such as <a class="link" href="#def_parent">parents</a>, committer, | |
| author, date and the <a class="link" href="#def_tree_object">tree object</a> which corresponds | |
| to the top <a class="link" href="#def_directory">directory</a> of the stored | |
| revision. | |
| </dd><dt><span class="term"><a name="def_commit-ish"></a>commit-ish (also committish)</span></dt><dd> | |
| A <a class="link" href="#def_commit_object">commit object</a> or an <a class="link" href="#def_object">object</a> that | |
| can be recursively <a class="link" href="#def_dereference">dereferenced</a> to a commit object. | |
| The following are all commit-ishes: | |
| a commit object, | |
| a <a class="link" href="#def_tag_object">tag object</a> that points to a commit | |
| object, | |
| a tag object that points to a tag object that points to a | |
| commit object, | |
| etc. | |
| </dd><dt><span class="term"><a name="def_core_git"></a>core Git</span></dt><dd> | |
| Fundamental data structures and utilities of Git. Exposes only limited | |
| source code management tools. | |
| </dd><dt><span class="term"><a name="def_DAG"></a>DAG</span></dt><dd> | |
| Directed acyclic graph. The <a class="link" href="#def_commit_object">commit objects</a> form a | |
| directed acyclic graph, because they have parents (directed), and the | |
| graph of commit objects is acyclic (there is no <a class="link" href="#def_chain">chain</a> | |
| which begins and ends with the same <a class="link" href="#def_object">object</a>). | |
| </dd><dt><span class="term"><a name="def_dangling_object"></a>dangling object</span></dt><dd> | |
| An <a class="link" href="#def_unreachable_object">unreachable object</a> which is not | |
| <a class="link" href="#def_reachable">reachable</a> even from other unreachable objects; a | |
| dangling object has no references to it from any | |
| reference or <a class="link" href="#def_object">object</a> in the <a class="link" href="#def_repository">repository</a>. | |
| </dd><dt><span class="term"><a name="def_dereference"></a>dereference</span></dt><dd> | |
| <p class="simpara">Referring to a <a class="link" href="#def_symref">symbolic ref</a>: the action of accessing the | |
| <a class="link" href="#def_ref">reference</a> pointed at by a symbolic ref. Recursive | |
| dereferencing involves repeating the aforementioned process on the | |
| resulting ref until a non-symbolic reference is found.</p> | |
| <p class="simpara">Referring to a <a class="link" href="#def_tag_object">tag object</a>: the action of accessing the | |
| <a class="link" href="#def_object">object</a> a tag points at. Tags are recursively dereferenced by | |
| repeating the operation on the result object until the result has either a | |
| specified <a class="link" href="#def_object_type">object type</a> (where applicable) or any non-"tag" | |
| object type. A synonym for "recursive dereference" in the context of tags is | |
| "<a class="link" href="#def_peel">peel</a>".</p> | |
| <p class="simpara">Referring to a <a class="link" href="#def_commit_object">commit object</a>: the action of accessing | |
| the commit’s tree object. Commits cannot be dereferenced recursively.</p> | |
| <p class="simpara">Unless otherwise specified, "dereferencing" as it used in the context of Git | |
| commands or protocols is implicitly recursive.</p> | |
| </dd><dt><span class="term"><a name="def_detached_HEAD"></a>detached HEAD</span></dt><dd> | |
| <p class="simpara">Normally the <a class="link" href="#def_HEAD">HEAD</a> stores the name of a | |
| <a class="link" href="#def_branch">branch</a>, and commands that operate on the | |
| history HEAD represents operate on the history leading to the | |
| tip of the branch the HEAD points at. However, Git also | |
| allows you to <a class="link" href="#def_checkout">check out</a> an arbitrary | |
| <a class="link" href="#def_commit">commit</a> that isn’t necessarily the tip of any | |
| particular branch. The HEAD in such a state is called | |
| "detached".</p> | |
| <p class="simpara">Note that commands that operate on the history of the current branch | |
| (e.g. <code class="literal">git</code> <code class="literal">commit</code> to build a new history on top of it) still work | |
| while the HEAD is detached. They update the HEAD to point at the tip | |
| of the updated history without affecting any branch. Commands that | |
| update or inquire information <span class="emphasis"><em>about</em></span> the current branch (e.g. <code class="literal">git</code> | |
| <code class="literal">branch</code> <code class="literal">--set-upstream-to</code> that sets what remote-tracking branch the | |
| current branch integrates with) obviously do not work, as there is no | |
| (real) current branch to ask about in this state.</p> | |
| </dd><dt><span class="term"><a name="def_directory"></a>directory</span></dt><dd> | |
| The list you get with "ls" :-) | |
| </dd><dt><span class="term"><a name="def_dirty"></a>dirty</span></dt><dd> | |
| A <a class="link" href="#def_working_tree">working tree</a> is said to be "dirty" if | |
| it contains modifications which have not been <a class="link" href="#def_commit">committed</a> to the current | |
| <a class="link" href="#def_branch">branch</a>. | |
| </dd><dt><span class="term"><a name="def_evil_merge"></a>evil merge</span></dt><dd> | |
| An evil merge is a <a class="link" href="#def_merge">merge</a> that introduces changes that | |
| do not appear in any <a class="link" href="#def_parent">parent</a>. | |
| </dd><dt><span class="term"><a name="def_fast_forward"></a>fast-forward</span></dt><dd> | |
| A fast-forward is a special type of <a class="link" href="#def_merge">merge</a> where you have a | |
| <a class="link" href="#def_revision">revision</a> and you are "merging" another | |
| <a class="link" href="#def_branch">branch</a>'s changes that happen to be a descendant of what | |
| you have. In such a case, you do not make a new <a class="link" href="#def_merge">merge</a> | |
| <a class="link" href="#def_commit">commit</a> but instead just update your branch to point at the same | |
| revision as the branch you are merging. This will happen frequently on a | |
| <a class="link" href="#def_remote_tracking_branch">remote-tracking branch</a> of a remote | |
| <a class="link" href="#def_repository">repository</a>. | |
| </dd><dt><span class="term"><a name="def_fetch"></a>fetch</span></dt><dd> | |
| Fetching a <a class="link" href="#def_branch">branch</a> means to get the | |
| branch’s <a class="link" href="#def_head_ref">head ref</a> from a remote | |
| <a class="link" href="#def_repository">repository</a>, to find out which objects are | |
| missing from the local <a class="link" href="#def_object_database">object database</a>, | |
| and to get them, too. See also <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a>. | |
| </dd><dt><span class="term"><a name="def_file_system"></a>file system</span></dt><dd> | |
| Linus Torvalds originally designed Git to be a user space file system, | |
| i.e. the infrastructure to hold files and directories. That ensured the | |
| efficiency and speed of Git. | |
| </dd><dt><span class="term"><a name="def_git_archive"></a>Git archive</span></dt><dd> | |
| Synonym for <a class="link" href="#def_repository">repository</a> (for arch people). | |
| </dd><dt><span class="term"><a name="def_gitfile"></a>gitfile</span></dt><dd> | |
| A plain file .<code class="literal">git</code> at the root of a working tree that | |
| points at the directory that is the real repository. | |
| For proper use see <a class="ulink" href="git-worktree.html" target="_top">git-worktree(1)</a> or <a class="ulink" href="git-submodule.html" target="_top">git-submodule(1)</a>. | |
| For syntax see <a class="ulink" href="gitrepository-layout.html" target="_top">gitrepository-layout(5)</a>. | |
| </dd><dt><span class="term"><a name="def_grafts"></a>grafts</span></dt><dd> | |
| <p class="simpara">Grafts enable two otherwise different lines of development to be joined | |
| together by recording fake ancestry information for commits. This way | |
| you can make Git pretend the set of <a class="link" href="#def_parent">parents</a> a <a class="link" href="#def_commit">commit</a> has | |
| is different from what was recorded when the commit was | |
| created. Configured via the .<code class="literal">git/info/grafts</code> file.</p> | |
| <p class="simpara">Note that the grafts mechanism is outdated and can lead to problems | |
| transferring objects between repositories; see <a class="ulink" href="git-replace.html" target="_top">git-replace(1)</a> | |
| for a more flexible and robust system to do the same thing.</p> | |
| </dd><dt><span class="term"><a name="def_hash"></a>hash</span></dt><dd> | |
| In Git’s context, synonym for <a class="link" href="#def_object_name">object name</a>. | |
| </dd><dt><span class="term"><a name="def_head"></a>head</span></dt><dd> | |
| A <a class="link" href="#def_ref">named reference</a> to the <a class="link" href="#def_commit">commit</a> at the tip of a | |
| <a class="link" href="#def_branch">branch</a>. Heads are stored in a file in | |
| <code class="literal">$GIT_DIR/refs/heads/</code> directory, except when using packed refs. (See | |
| <a class="ulink" href="git-pack-refs.html" target="_top">git-pack-refs(1)</a>.) | |
| </dd><dt><span class="term"><a name="def_HEAD"></a>HEAD</span></dt><dd> | |
| The current <a class="link" href="#def_branch">branch</a>. In more detail: Your <a class="link" href="#def_working_tree">working tree</a> is normally derived from the state of the tree | |
| referred to by HEAD. HEAD is a reference to one of the | |
| <a class="link" href="#def_head">heads</a> in your repository, except when using a | |
| <a class="link" href="#def_detached_HEAD">detached HEAD</a>, in which case it directly | |
| references an arbitrary commit. | |
| </dd><dt><span class="term"><a name="def_head_ref"></a>head ref</span></dt><dd> | |
| A synonym for <a class="link" href="#def_head">head</a>. | |
| </dd><dt><span class="term"><a name="def_hook"></a>hook</span></dt><dd> | |
| During the normal execution of several Git commands, call-outs are made | |
| to optional scripts that allow a developer to add functionality or | |
| checking. Typically, the hooks allow for a command to be pre-verified | |
| and potentially aborted, and allow for a post-notification after the | |
| operation is done. The hook scripts are found in the | |
| <code class="literal">$GIT_DIR/hooks/</code> directory, and are enabled by simply | |
| removing the .<code class="literal">sample</code> suffix from the filename. In earlier versions | |
| of Git you had to make them executable. | |
| </dd><dt><span class="term"><a name="def_index"></a>index</span></dt><dd> | |
| A collection of files with stat information, whose contents are stored | |
| as objects. The index is a stored version of your | |
| <a class="link" href="#def_working_tree">working tree</a>. Truth be told, it can also contain a second, and even | |
| a third version of a working tree, which are used | |
| when <a class="link" href="#def_merge">merging</a>. | |
| </dd><dt><span class="term"><a name="def_index_entry"></a>index entry</span></dt><dd> | |
| The information regarding a particular file, stored in the | |
| <a class="link" href="#def_index">index</a>. An index entry can be unmerged, if a | |
| <a class="link" href="#def_merge">merge</a> was started, but not yet finished (i.e. if | |
| the index contains multiple versions of that file). | |
| </dd><dt><span class="term"><a name="def_master"></a>master</span></dt><dd> | |
| The default development <a class="link" href="#def_branch">branch</a>. Whenever you | |
| create a Git <a class="link" href="#def_repository">repository</a>, a branch named | |
| "master" is created, and becomes the active branch. In most | |
| cases, this contains the local development, though that is | |
| purely by convention and is not required. | |
| </dd><dt><span class="term"><a name="def_merge"></a>merge</span></dt><dd> | |
| <p class="simpara">As a verb: To bring the contents of another | |
| <a class="link" href="#def_branch">branch</a> (possibly from an external | |
| <a class="link" href="#def_repository">repository</a>) into the current branch. In the | |
| case where the merged-in branch is from a different repository, | |
| this is done by first <a class="link" href="#def_fetch">fetching</a> the remote branch | |
| and then merging the result into the current branch. This | |
| combination of fetch and merge operations is called a | |
| <a class="link" href="#def_pull">pull</a>. Merging is performed by an automatic process | |
| that identifies changes made since the branches diverged, and | |
| then applies all those changes together. In cases where changes | |
| conflict, manual intervention may be required to complete the | |
| merge.</p> | |
| <p class="simpara">As a noun: unless it is a <a class="link" href="#def_fast_forward">fast-forward</a>, a | |
| successful merge results in the creation of a new <a class="link" href="#def_commit">commit</a> | |
| representing the result of the merge, and having as | |
| <a class="link" href="#def_parent">parents</a> the tips of the merged <a class="link" href="#def_branch">branches</a>. | |
| This commit is referred to as a "merge commit", or sometimes just a | |
| "merge".</p> | |
| </dd><dt><span class="term"><a name="def_object"></a>object</span></dt><dd> | |
| The unit of storage in Git. It is uniquely identified by the | |
| <a class="link" href="#def_SHA1">SHA-1</a> of its contents. Consequently, an | |
| object cannot be changed. | |
| </dd><dt><span class="term"><a name="def_object_database"></a>object database</span></dt><dd> | |
| Stores a set of "objects", and an individual <a class="link" href="#def_object">object</a> is | |
| identified by its <a class="link" href="#def_object_name">object name</a>. The objects usually | |
| live in <code class="literal">$GIT_DIR/objects/</code>. | |
| </dd><dt><span class="term"><a name="def_object_identifier"></a>object identifier, object ID, oid</span></dt><dd> | |
| Synonyms for <a class="link" href="#def_object_name">object name</a>. | |
| </dd><dt><span class="term"><a name="def_object_name"></a>object name</span></dt><dd> | |
| The unique identifier of an <a class="link" href="#def_object">object</a>. The | |
| object name is usually represented by a 40 character | |
| hexadecimal string. Also colloquially called <a class="link" href="#def_SHA1">SHA-1</a>. | |
| </dd><dt><span class="term"><a name="def_object_type"></a>object type</span></dt><dd> | |
| One of the identifiers "<a class="link" href="#def_commit_object">commit</a>", | |
| "<a class="link" href="#def_tree_object">tree</a>", "<a class="link" href="#def_tag_object">tag</a>" or | |
| "<a class="link" href="#def_blob_object">blob</a>" describing the type of an | |
| <a class="link" href="#def_object">object</a>. | |
| </dd><dt><span class="term"><a name="def_octopus"></a>octopus</span></dt><dd> | |
| To <a class="link" href="#def_merge">merge</a> more than two <a class="link" href="#def_branch">branches</a>. | |
| </dd><dt><span class="term"><a name="def_orphan"></a>orphan</span></dt><dd> | |
| The act of getting on a <a class="link" href="#def_branch">branch</a> that does not | |
| exist yet (i.e., an <a class="link" href="#def_unborn">unborn</a> branch). After | |
| such an operation, the commit first created becomes a commit | |
| without a parent, starting a new history. | |
| </dd><dt><span class="term"><a name="def_origin"></a>origin</span></dt><dd> | |
| The default upstream <a class="link" href="#def_repository">repository</a>. Most projects have | |
| at least one upstream project which they track. By default | |
| <span class="emphasis"><em>origin</em></span> is used for that purpose. New upstream updates | |
| will be fetched into <a class="link" href="#def_remote_tracking_branch">remote-tracking branches</a> named | |
| origin/name-of-upstream-branch, which you can see using | |
| <code class="literal">git</code> <code class="literal">branch</code> <code class="literal">-r</code>. | |
| </dd><dt><span class="term"><a name="def_overlay"></a>overlay</span></dt><dd> | |
| Only update and add files to the working directory, but don’t | |
| delete them, similar to how <span class="emphasis"><em>cp -R</em></span> would update the contents | |
| in the destination directory. This is the default mode in a | |
| <a class="link" href="#def_checkout">checkout</a> when checking out files from the | |
| <a class="link" href="#def_index">index</a> or a <a class="link" href="#def_tree-ish">tree-ish</a>. In | |
| contrast, no-overlay mode also deletes tracked files not | |
| present in the source, similar to <span class="emphasis"><em>rsync --delete</em></span>. | |
| </dd><dt><span class="term"><a name="def_pack"></a>pack</span></dt><dd> | |
| A set of objects which have been compressed into one file (to save space | |
| or to transmit them efficiently). | |
| </dd><dt><span class="term"><a name="def_pack_index"></a>pack index</span></dt><dd> | |
| The list of identifiers, and other information, of the objects in a | |
| <a class="link" href="#def_pack">pack</a>, to assist in efficiently accessing the contents of a | |
| pack. | |
| </dd><dt><span class="term"><a name="def_pathspec"></a>pathspec</span></dt><dd> | |
| <p class="simpara">Pattern used to limit paths in Git commands.</p> | |
| <p class="simpara">Pathspecs are used on the command line of "git ls-files", "git | |
| ls-tree", "git add", "git grep", "git diff", "git checkout", | |
| and many other commands to | |
| limit the scope of operations to some subset of the tree or | |
| working tree. See the documentation of each command for whether | |
| paths are relative to the current directory or toplevel. The | |
| pathspec syntax is as follows:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| any path matches itself | |
| </li><li class="listitem"> | |
| the pathspec up to the last slash represents a | |
| directory prefix. The scope of that pathspec is | |
| limited to that subtree. | |
| </li><li class="listitem"> | |
| the rest of the pathspec is a pattern for the remainder | |
| of the pathname. Paths relative to the directory | |
| prefix will be matched against that pattern using fnmatch(3); | |
| in particular, <span class="emphasis"><em>*</em></span> and <span class="emphasis"><em>?</em></span> <span class="emphasis"><em>can</em></span> match directory separators. | |
| </li></ul></div> | |
| <p class="simpara">For example, Documentation/*.jpg will match all .jpg files | |
| in the Documentation subtree, | |
| including Documentation/chapter_1/figure_1.jpg.</p> | |
| <p class="simpara">A pathspec that begins with a colon <code class="literal">:</code> has special meaning. In the | |
| short form, the leading colon <code class="literal">:</code> is followed by zero or more "magic | |
| signature" letters (which optionally is terminated by another colon <code class="literal">:</code>), | |
| and the remainder is the pattern to match against the path. | |
| The "magic signature" consists of ASCII symbols that are neither | |
| alphanumeric, glob, regex special characters nor colon. | |
| The optional colon that terminates the "magic signature" can be | |
| omitted if the pattern begins with a character that does not belong to | |
| "magic signature" symbol set and is not a colon.</p> | |
| <p class="simpara">In the long form, the leading colon <code class="literal">:</code> is followed by an open | |
| parenthesis (, a comma-separated list of zero or more "magic words", | |
| and a close parentheses ), and the remainder is the pattern to match | |
| against the path.</p> | |
| <p class="simpara">A pathspec with only a colon means "there is no pathspec". This form | |
| should not be combined with other pathspec.</p> | |
| <div class="variablelist"><dl class="variablelist"><dt><span class="term">top</span></dt><dd> | |
| The magic word <code class="literal">top</code> (magic signature: <code class="literal">/</code>) makes the pattern | |
| match from the root of the working tree, even when you are | |
| running the command from inside a subdirectory. | |
| </dd><dt><span class="term">literal</span></dt><dd> | |
| Wildcards in the pattern such as <code class="literal">*</code> or ? are treated | |
| as literal characters. | |
| </dd><dt><span class="term">icase</span></dt><dd> | |
| Case insensitive match. | |
| </dd><dt><span class="term">glob</span></dt><dd> | |
| <p class="simpara">Git treats the pattern as a shell glob suitable for | |
| consumption by fnmatch(3) with the FNM_PATHNAME flag: | |
| wildcards in the pattern will not match a / in the pathname. | |
| For example, "Documentation/*.html" matches | |
| "Documentation/git.html" but not "Documentation/ppc/ppc.html" | |
| or "tools/perf/Documentation/perf.html".</p> | |
| <p class="simpara">Two consecutive asterisks ("<code class="literal">**</code>") in patterns matched against | |
| full pathname may have special meaning:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| A leading "<code class="literal">**</code>" followed by a slash means match in all | |
| directories. For example, "<code class="literal">**/foo</code>" matches file or directory | |
| "<code class="literal">foo</code>" anywhere. "<code class="literal">**/foo/bar</code>" matches file or directory "<code class="literal">bar</code>" | |
| anywhere that is directly under directory "<code class="literal">foo</code>". | |
| </li><li class="listitem"> | |
| A trailing "<code class="literal">/**</code>" matches everything inside. For example, | |
| "<code class="literal">abc/**</code>" matches all files inside directory "abc", relative | |
| to the location of the .<code class="literal">gitignore</code> file, with infinite depth. | |
| </li><li class="listitem"> | |
| A slash followed by two consecutive asterisks then a slash | |
| matches zero or more directories. For example, "<code class="literal">a/**/b</code>" | |
| matches "<code class="literal">a/b</code>", "<code class="literal">a/x/b</code>", "<code class="literal">a/x/y/b</code>" and so on. | |
| </li><li class="listitem"> | |
| Other consecutive asterisks are considered invalid. | |
| </li></ul></div> | |
| <p class="simpara">Glob magic is incompatible with literal magic.</p> | |
| </dd><dt><span class="term">attr</span></dt><dd> | |
| <p class="simpara">After <code class="literal">attr:</code> comes a space separated list of "attribute | |
| requirements", all of which must be met in order for the | |
| path to be considered a match; this is in addition to the | |
| usual non-magic pathspec pattern matching. | |
| See <a class="ulink" href="gitattributes.html" target="_top">gitattributes(5)</a>.</p> | |
| <p class="simpara">Each of the attribute requirements for the path takes one of | |
| these forms:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| "<code class="literal">ATTR</code>" requires that the attribute <code class="literal">ATTR</code> be set. | |
| </li><li class="listitem"> | |
| "<code class="literal">-ATTR</code>" requires that the attribute <code class="literal">ATTR</code> be unset. | |
| </li><li class="listitem"> | |
| "<code class="literal">ATTR=VALUE</code>" requires that the attribute <code class="literal">ATTR</code> be | |
| set to the string <code class="literal">VALUE</code>. | |
| </li><li class="listitem"> | |
| "!ATTR" requires that the attribute <code class="literal">ATTR</code> be | |
| unspecified. | |
| </li></ul></div> | |
| <p class="simpara">Note that when matching against a tree object, attributes are still | |
| obtained from working tree, not from the given tree object.</p> | |
| </dd><dt><span class="term">exclude</span></dt><dd> | |
| After a path matches any non-exclude pathspec, it will be run | |
| through all exclude pathspecs (magic signature: ! or its | |
| synonym <code class="literal">^</code>). If it matches, the path is ignored. When there | |
| is no non-exclude pathspec, the exclusion is applied to the | |
| result set as if invoked without any pathspec. | |
| </dd></dl></div> | |
| </dd><dt><span class="term"><a name="def_parent"></a>parent</span></dt><dd> | |
| A <a class="link" href="#def_commit_object">commit object</a> contains a (possibly empty) list | |
| of the logical predecessor(s) in the line of development, i.e. its | |
| parents. | |
| </dd><dt><span class="term"><a name="def_peel"></a>peel</span></dt><dd> | |
| The action of recursively <a class="link" href="#def_dereference">dereferencing</a> a | |
| <a class="link" href="#def_tag_object">tag object</a>. | |
| </dd><dt><span class="term"><a name="def_pickaxe"></a>pickaxe</span></dt><dd> | |
| The term <a class="link" href="#def_pickaxe">pickaxe</a> refers to an option to the diffcore | |
| routines that help select changes that add or delete a given text | |
| string. With the <code class="literal">--pickaxe-all</code> option, it can be used to view the full | |
| <a class="link" href="#def_changeset">changeset</a> that introduced or removed, say, a | |
| particular line of text. See <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a>. | |
| </dd><dt><span class="term"><a name="def_plumbing"></a>plumbing</span></dt><dd> | |
| Cute name for <a class="link" href="#def_core_git">core Git</a>. | |
| </dd><dt><span class="term"><a name="def_porcelain"></a>porcelain</span></dt><dd> | |
| Cute name for programs and program suites depending on | |
| <a class="link" href="#def_core_git">core Git</a>, presenting a high level access to | |
| core Git. Porcelains expose more of a <a class="link" href="#def_SCM">SCM</a> | |
| interface than the <a class="link" href="#def_plumbing">plumbing</a>. | |
| </dd><dt><span class="term"><a name="def_per_worktree_ref"></a>per-worktree ref</span></dt><dd> | |
| Refs that are per-<a class="link" href="#def_worktree">worktree</a>, rather than | |
| global. This is presently only <a class="link" href="#def_HEAD">HEAD</a> and any refs | |
| that start with <code class="literal">refs/bisect/</code>, but might later include other | |
| unusual refs. | |
| </dd><dt><span class="term"><a name="def_pseudoref"></a>pseudoref</span></dt><dd> | |
| <p class="simpara">A ref that has different semantics than normal refs. These refs can be | |
| read via normal Git commands, but cannot be written to by commands like | |
| <a class="ulink" href="git-update-ref.html" target="_top">git-update-ref(1)</a>.</p> | |
| <p class="simpara">The following pseudorefs are known to Git:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| <code class="literal">FETCH_HEAD</code> is written by <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a> or <a class="ulink" href="git-pull.html" target="_top">git-pull(1)</a>. It | |
| may refer to multiple object IDs. Each object ID is annotated with metadata | |
| indicating where it was fetched from and its fetch status. | |
| </li><li class="listitem"> | |
| <code class="literal">MERGE_HEAD</code> is written by <a class="ulink" href="git-merge.html" target="_top">git-merge(1)</a> when resolving merge | |
| conflicts. It contains all commit IDs which are being merged. | |
| </li></ul></div> | |
| </dd><dt><span class="term"><a name="def_pull"></a>pull</span></dt><dd> | |
| Pulling a <a class="link" href="#def_branch">branch</a> means to <a class="link" href="#def_fetch">fetch</a> it and | |
| <a class="link" href="#def_merge">merge</a> it. See also <a class="ulink" href="git-pull.html" target="_top">git-pull(1)</a>. | |
| </dd><dt><span class="term"><a name="def_push"></a>push</span></dt><dd> | |
| Pushing a <a class="link" href="#def_branch">branch</a> means to get the branch’s | |
| <a class="link" href="#def_head_ref">head ref</a> from a remote <a class="link" href="#def_repository">repository</a>, | |
| find out if it is an ancestor to the branch’s local | |
| head ref, and in that case, putting all | |
| objects, which are <a class="link" href="#def_reachable">reachable</a> from the local | |
| head ref, and which are missing from the remote | |
| repository, into the remote | |
| <a class="link" href="#def_object_database">object database</a>, and updating the remote | |
| head ref. If the remote <a class="link" href="#def_head">head</a> is not an | |
| ancestor to the local head, the push fails. | |
| </dd><dt><span class="term"><a name="def_reachable"></a>reachable</span></dt><dd> | |
| All of the ancestors of a given <a class="link" href="#def_commit">commit</a> are said to be | |
| "reachable" from that commit. More | |
| generally, one <a class="link" href="#def_object">object</a> is reachable from | |
| another if we can reach the one from the other by a <a class="link" href="#def_chain">chain</a> | |
| that follows <a class="link" href="#def_tag">tags</a> to whatever they tag, | |
| <a class="link" href="#def_commit_object">commits</a> to their parents or trees, and | |
| <a class="link" href="#def_tree_object">trees</a> to the trees or <a class="link" href="#def_blob_object">blobs</a> | |
| that they contain. | |
| </dd><dt><span class="term"><a name="def_reachability_bitmap"></a>reachability bitmaps</span></dt><dd> | |
| Reachability bitmaps store information about the | |
| <a class="link" href="#def_reachable">reachability</a> of a selected set of commits in | |
| a packfile, or a multi-pack index (MIDX), to speed up object search. | |
| The bitmaps are stored in a ".bitmap" file. A repository may have at | |
| most one bitmap file in use. The bitmap file may belong to either one | |
| pack, or the repository’s multi-pack index (if it exists). | |
| </dd><dt><span class="term"><a name="def_rebase"></a>rebase</span></dt><dd> | |
| To reapply a series of changes from a <a class="link" href="#def_branch">branch</a> to a | |
| different base, and reset the <a class="link" href="#def_head">head</a> of that branch | |
| to the result. | |
| </dd><dt><span class="term"><a name="def_ref"></a>ref</span></dt><dd> | |
| <p class="simpara">A name that points to an <a class="link" href="#def_object_name">object name</a> or | |
| another ref (the latter is called a <a class="link" href="#def_symref">symbolic ref</a>). | |
| For convenience, a ref can sometimes be abbreviated when used | |
| as an argument to a Git command; see <a class="ulink" href="gitrevisions.html" target="_top">gitrevisions(7)</a> | |
| for details. | |
| Refs are stored in the <a class="link" href="#def_repository">repository</a>.</p> | |
| <p class="simpara">The ref namespace is hierarchical. | |
| Ref names must either start with <code class="literal">refs/</code> or be located in the root of | |
| the hierarchy. For the latter, their name must follow these rules:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| The name consists of only upper-case characters or underscores. | |
| </li><li class="listitem"> | |
| The name ends with "<code class="literal">_HEAD</code>" or is equal to "<code class="literal">HEAD</code>". | |
| </li></ul></div> | |
| <p class="simpara">There are some irregular refs in the root of the hierarchy that do not | |
| match these rules. The following list is exhaustive and shall not be | |
| extended in the future:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| <code class="literal">AUTO_MERGE</code> | |
| </li><li class="listitem"> | |
| <code class="literal">BISECT_EXPECTED_REV</code> | |
| </li><li class="listitem"> | |
| <code class="literal">NOTES_MERGE_PARTIAL</code> | |
| </li><li class="listitem"> | |
| <code class="literal">NOTES_MERGE_REF</code> | |
| </li><li class="listitem"> | |
| <code class="literal">MERGE_AUTOSTASH</code> | |
| </li></ul></div> | |
| <p class="simpara">Different subhierarchies are used for different purposes. For example, | |
| the <code class="literal">refs/heads/</code> hierarchy is used to represent local branches whereas | |
| the <code class="literal">refs/tags/</code> hierarchy is used to represent local tags..</p> | |
| </dd><dt><span class="term"><a name="def_reflog"></a>reflog</span></dt><dd> | |
| A reflog shows the local "history" of a ref. In other words, | |
| it can tell you what the 3rd last revision in <span class="emphasis"><em>this</em></span> repository | |
| was, and what was the current state in <span class="emphasis"><em>this</em></span> repository, | |
| yesterday 9:14pm. See <a class="ulink" href="git-reflog.html" target="_top">git-reflog(1)</a> for details. | |
| </dd><dt><span class="term"><a name="def_refspec"></a>refspec</span></dt><dd> | |
| A "refspec" is used by <a class="link" href="#def_fetch">fetch</a> and | |
| <a class="link" href="#def_push">push</a> to describe the mapping between remote | |
| <a class="link" href="#def_ref">ref</a> and local ref. See <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a> or | |
| <a class="ulink" href="git-push.html" target="_top">git-push(1)</a> for details. | |
| </dd><dt><span class="term"><a name="def_remote"></a>remote repository</span></dt><dd> | |
| A <a class="link" href="#def_repository">repository</a> which is used to track the same | |
| project but resides somewhere else. To communicate with remotes, | |
| see <a class="link" href="#def_fetch">fetch</a> or <a class="link" href="#def_push">push</a>. | |
| </dd><dt><span class="term"><a name="def_remote_tracking_branch"></a>remote-tracking branch</span></dt><dd> | |
| A <a class="link" href="#def_ref">ref</a> that is used to follow changes from another | |
| <a class="link" href="#def_repository">repository</a>. It typically looks like | |
| <span class="emphasis"><em>refs/remotes/foo/bar</em></span> (indicating that it tracks a branch named | |
| <span class="emphasis"><em>bar</em></span> in a remote named <span class="emphasis"><em>foo</em></span>), and matches the right-hand-side of | |
| a configured fetch <a class="link" href="#def_refspec">refspec</a>. A remote-tracking | |
| branch should not contain direct modifications or have local | |
| commits made to it. | |
| </dd><dt><span class="term"><a name="def_repository"></a>repository</span></dt><dd> | |
| A collection of <a class="link" href="#def_ref">refs</a> together with an | |
| <a class="link" href="#def_object_database">object database</a> containing all objects | |
| which are <a class="link" href="#def_reachable">reachable</a> from the refs, possibly | |
| accompanied by meta data from one or more <a class="link" href="#def_porcelain">porcelains</a>. A | |
| repository can share an object database with other repositories | |
| via <a class="link" href="#def_alternate_object_database">alternates mechanism</a>. | |
| </dd><dt><span class="term"><a name="def_resolve"></a>resolve</span></dt><dd> | |
| The action of fixing up manually what a failed automatic | |
| <a class="link" href="#def_merge">merge</a> left behind. | |
| </dd><dt><span class="term"><a name="def_revision"></a>revision</span></dt><dd> | |
| Synonym for <a class="link" href="#def_commit">commit</a> (the noun). | |
| </dd><dt><span class="term"><a name="def_rewind"></a>rewind</span></dt><dd> | |
| To throw away part of the development, i.e. to assign the | |
| <a class="link" href="#def_head">head</a> to an earlier <a class="link" href="#def_revision">revision</a>. | |
| </dd><dt><span class="term"><a name="def_SCM"></a>SCM</span></dt><dd> | |
| Source code management (tool). | |
| </dd><dt><span class="term"><a name="def_SHA1"></a>SHA-1</span></dt><dd> | |
| "Secure Hash Algorithm 1"; a cryptographic hash function. | |
| In the context of Git used as a synonym for <a class="link" href="#def_object_name">object name</a>. | |
| </dd><dt><span class="term"><a name="def_shallow_clone"></a>shallow clone</span></dt><dd> | |
| Mostly a synonym to <a class="link" href="#def_shallow_repository">shallow repository</a> | |
| but the phrase makes it more explicit that it was created by | |
| running <code class="literal">git</code> <code class="literal">clone</code> <code class="literal">--depth=..</code>. command. | |
| </dd><dt><span class="term"><a name="def_shallow_repository"></a>shallow repository</span></dt><dd> | |
| A shallow <a class="link" href="#def_repository">repository</a> has an incomplete | |
| history some of whose <a class="link" href="#def_commit">commits</a> have <a class="link" href="#def_parent">parents</a> cauterized away (in other | |
| words, Git is told to pretend that these commits do not have the | |
| parents, even though they are recorded in the <a class="link" href="#def_commit_object">commit | |
| object</a>). This is sometimes useful when you are interested only in the | |
| recent history of a project even though the real history recorded in the | |
| upstream is much larger. A shallow repository | |
| is created by giving the <code class="literal">--depth</code> option to <a class="ulink" href="git-clone.html" target="_top">git-clone(1)</a>, and | |
| its history can be later deepened with <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a>. | |
| </dd><dt><span class="term"><a name="def_stash"></a>stash entry</span></dt><dd> | |
| An <a class="link" href="#def_object">object</a> used to temporarily store the contents of a | |
| <a class="link" href="#def_dirty">dirty</a> working directory and the index for future reuse. | |
| </dd><dt><span class="term"><a name="def_submodule"></a>submodule</span></dt><dd> | |
| A <a class="link" href="#def_repository">repository</a> that holds the history of a | |
| separate project inside another repository (the latter of | |
| which is called <a class="link" href="#def_superproject">superproject</a>). | |
| </dd><dt><span class="term"><a name="def_superproject"></a>superproject</span></dt><dd> | |
| A <a class="link" href="#def_repository">repository</a> that references repositories | |
| of other projects in its working tree as <a class="link" href="#def_submodule">submodules</a>. | |
| The superproject knows about the names of (but does not hold | |
| copies of) commit objects of the contained submodules. | |
| </dd><dt><span class="term"><a name="def_symref"></a>symref</span></dt><dd> | |
| Symbolic reference: instead of containing the <a class="link" href="#def_SHA1">SHA-1</a> id | |
| itself, it is of the format <span class="emphasis"><em>ref: refs/some/thing</em></span> and when referenced, | |
| it recursively <a class="link" href="#def_dereference">dereferences</a> to this reference. | |
| <span class="emphasis"><em><a class="link" href="#def_HEAD">HEAD</a></em></span> is a prime example of a symref. Symbolic references | |
| are manipulated with the <a class="ulink" href="git-symbolic-ref.html" target="_top">git-symbolic-ref(1)</a> command. | |
| </dd><dt><span class="term"><a name="def_tag"></a>tag</span></dt><dd> | |
| A <a class="link" href="#def_ref">ref</a> under <code class="literal">refs/tags/</code> namespace that points to an | |
| object of an arbitrary type (typically a tag points to either a | |
| <a class="link" href="#def_tag_object">tag</a> or a <a class="link" href="#def_commit_object">commit object</a>). | |
| In contrast to a <a class="link" href="#def_head">head</a>, a tag is not updated by | |
| the <code class="literal">commit</code> command. A Git tag has nothing to do with a Lisp | |
| tag (which would be called an <a class="link" href="#def_object_type">object type</a> | |
| in Git’s context). A tag is most typically used to mark a particular | |
| point in the commit ancestry <a class="link" href="#def_chain">chain</a>. | |
| </dd><dt><span class="term"><a name="def_tag_object"></a>tag object</span></dt><dd> | |
| An <a class="link" href="#def_object">object</a> containing a <a class="link" href="#def_ref">ref</a> pointing to | |
| another object, which can contain a message just like a | |
| <a class="link" href="#def_commit_object">commit object</a>. It can also contain a (PGP) | |
| signature, in which case it is called a "signed tag object". | |
| </dd><dt><span class="term"><a name="def_topic_branch"></a>topic branch</span></dt><dd> | |
| A regular Git <a class="link" href="#def_branch">branch</a> that is used by a developer to | |
| identify a conceptual line of development. Since branches are very easy | |
| and inexpensive, it is often desirable to have several small branches | |
| that each contain very well defined concepts or small incremental yet | |
| related changes. | |
| </dd><dt><span class="term"><a name="def_trailer"></a>trailer</span></dt><dd> | |
| Key-value metadata. Trailers are optionally found at the end of | |
| a commit message. Might be called "footers" or "tags" in other | |
| communities. See <a class="ulink" href="git-interpret-trailers.html" target="_top">git-interpret-trailers(1)</a>. | |
| </dd><dt><span class="term"><a name="def_tree"></a>tree</span></dt><dd> | |
| Either a <a class="link" href="#def_working_tree">working tree</a>, or a <a class="link" href="#def_tree_object">tree | |
| object</a> together with the dependent <a class="link" href="#def_blob_object">blob</a> and tree objects | |
| (i.e. a stored representation of a working tree). | |
| </dd><dt><span class="term"><a name="def_tree_object"></a>tree object</span></dt><dd> | |
| An <a class="link" href="#def_object">object</a> containing a list of file names and modes along | |
| with refs to the associated blob and/or tree objects. A | |
| <a class="link" href="#def_tree">tree</a> is equivalent to a <a class="link" href="#def_directory">directory</a>. | |
| </dd><dt><span class="term"><a name="def_tree-ish"></a>tree-ish (also treeish)</span></dt><dd> | |
| A <a class="link" href="#def_tree_object">tree object</a> or an <a class="link" href="#def_object">object</a> that can | |
| be recursively <a class="link" href="#def_dereference">dereferenced</a> to a tree object. | |
| Dereferencing a <a class="link" href="#def_commit_object">commit object</a> yields the tree | |
| object corresponding to the <a class="link" href="#def_revision">revision</a>'s top | |
| <a class="link" href="#def_directory">directory</a>. | |
| The following are all tree-ishes: | |
| a <a class="link" href="#def_commit-ish">commit-ish</a>, | |
| a tree object, | |
| a <a class="link" href="#def_tag_object">tag object</a> that points to a tree object, | |
| a tag object that points to a tag object that points to a tree | |
| object, | |
| etc. | |
| </dd><dt><span class="term"><a name="def_unborn"></a>unborn</span></dt><dd> | |
| The <a class="link" href="#def_HEAD">HEAD</a> can point at a <a class="link" href="#def_branch">branch</a> | |
| that does not yet exist and that does not have any commit on | |
| it yet, and such a branch is called an unborn branch. The | |
| most typical way users encounter an unborn branch is by | |
| creating a repository anew without cloning from elsewhere. | |
| The HEAD would point at the <span class="emphasis"><em>main</em></span> (or <span class="emphasis"><em>master</em></span>, depending | |
| on your configuration) branch that is yet to be born. Also | |
| some operations can get you on an unborn branch with their | |
| <a class="link" href="#def_orphan">orphan</a> option. | |
| </dd><dt><span class="term"><a name="def_unmerged_index"></a>unmerged index</span></dt><dd> | |
| An <a class="link" href="#def_index">index</a> which contains unmerged | |
| <a class="link" href="#def_index_entry">index entries</a>. | |
| </dd><dt><span class="term"><a name="def_unreachable_object"></a>unreachable object</span></dt><dd> | |
| An <a class="link" href="#def_object">object</a> which is not <a class="link" href="#def_reachable">reachable</a> from a | |
| <a class="link" href="#def_branch">branch</a>, <a class="link" href="#def_tag">tag</a>, or any other reference. | |
| </dd><dt><span class="term"><a name="def_upstream_branch"></a>upstream branch</span></dt><dd> | |
| The default <a class="link" href="#def_branch">branch</a> that is merged into the branch in | |
| question (or the branch in question is rebased onto). It is configured | |
| via branch.<name>.remote and branch.<name>.merge. If the upstream branch | |
| of <span class="emphasis"><em>A</em></span> is <span class="emphasis"><em>origin/B</em></span> sometimes we say "<span class="emphasis"><em>A</em></span> is tracking <span class="emphasis"><em>origin/B</em></span>". | |
| </dd><dt><span class="term"><a name="def_working_tree"></a>working tree</span></dt><dd> | |
| The tree of actual checked out files. The working tree normally | |
| contains the contents of the <a class="link" href="#def_HEAD">HEAD</a> commit’s tree, | |
| plus any local changes that you have made but not yet committed. | |
| </dd><dt><span class="term"><a name="def_worktree"></a>worktree</span></dt><dd> | |
| A repository can have zero (i.e. bare repository) or one or | |
| more worktrees attached to it. One "worktree" consists of a | |
| "working tree" and repository metadata, most of which are | |
| shared among other worktrees of a single repository, and | |
| some of which are maintained separately per worktree | |
| (e.g. the index, HEAD and pseudorefs like MERGE_HEAD, | |
| per-worktree refs and per-worktree configuration file). | |
| </dd></dl></div> | |
| </div> | |
| </div> | |
| <div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a name="git-quick-start"></a>Appendix A. Git Quick Reference</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#quick-creating-a-new-repository">Creating a new repository</a></span></dt><dt><span class="section"><a href="#managing-branches">Managing branches</a></span></dt><dt><span class="section"><a href="#exploring-history">Exploring history</a></span></dt><dt><span class="section"><a href="#making-changes">Making changes</a></span></dt><dt><span class="section"><a href="#merging">Merging</a></span></dt><dt><span class="section"><a href="#sharing-your-changes">Sharing your changes</a></span></dt><dt><span class="section"><a href="#repository-maintenance">Repository maintenance</a></span></dt></dl></div> | |
| <p>This is a quick summary of the major commands; the previous chapters | |
| explain how these work in more detail.</p> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="quick-creating-a-new-repository"></a>Creating a new repository</h2></div></div></div> | |
| <p>From a tarball:</p> | |
| <pre class="screen">$ tar xzf project.tar.gz | |
| $ cd project | |
| $ git init | |
| Initialized empty Git repository in .git/ | |
| $ git add . | |
| $ git commit</pre> | |
| <p>From a remote repository:</p> | |
| <pre class="screen">$ git clone git://example.com/pub/project.git | |
| $ cd project</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="managing-branches"></a>Managing branches</h2></div></div></div> | |
| <pre class="screen">$ git branch # list all local branches in this repo | |
| $ git switch test # switch working directory to branch "test" | |
| $ git branch new # create branch "new" starting at current HEAD | |
| $ git branch -d new # delete branch "new"</pre> | |
| <p>Instead of basing a new branch on current HEAD (the default), use:</p> | |
| <pre class="screen">$ git branch new test # branch named "test" | |
| $ git branch new v2.6.15 # tag named v2.6.15 | |
| $ git branch new HEAD^ # commit before the most recent | |
| $ git branch new HEAD^^ # commit before that | |
| $ git branch new test~10 # ten commits before tip of branch "test"</pre> | |
| <p>Create and switch to a new branch at the same time:</p> | |
| <pre class="screen">$ git switch -c new v2.6.15</pre> | |
| <p>Update and examine branches from the repository you cloned from:</p> | |
| <pre class="screen">$ git fetch # update | |
| $ git branch -r # list | |
| origin/master | |
| origin/next | |
| ... | |
| $ git switch -c masterwork origin/master</pre> | |
| <p>Fetch a branch from a different repository, and give it a new | |
| name in your repository:</p> | |
| <pre class="screen">$ git fetch git://example.com/project.git theirbranch:mybranch | |
| $ git fetch git://example.com/project.git v2.6.15:mybranch</pre> | |
| <p>Keep a list of repositories you work with regularly:</p> | |
| <pre class="screen">$ git remote add example git://example.com/project.git | |
| $ git remote # list remote repositories | |
| example | |
| origin | |
| $ git remote show example # get details | |
| * remote example | |
| URL: git://example.com/project.git | |
| Tracked remote branches | |
| master | |
| next | |
| ... | |
| $ git fetch example # update branches from example | |
| $ git branch -r # list all remote branches</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="exploring-history"></a>Exploring history</h2></div></div></div> | |
| <pre class="screen">$ gitk # visualize and browse history | |
| $ git log # list all commits | |
| $ git log src/ # ...modifying src/ | |
| $ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15 | |
| $ git log master..test # ...in branch test, not in branch master | |
| $ git log test..master # ...in branch master, but not in test | |
| $ git log test...master # ...in one branch, not in both | |
| $ git log -S'foo()' # ...where difference contain "foo()" | |
| $ git log --since="2 weeks ago" | |
| $ git log -p # show patches as well | |
| $ git show # most recent commit | |
| $ git diff v2.6.15..v2.6.16 # diff between two tagged versions | |
| $ git diff v2.6.15..HEAD # diff with current head | |
| $ git grep "foo()" # search working directory for "foo()" | |
| $ git grep "foo()" v2.6.15 # search old tree for "foo()" | |
| $ git show v2.6.15:a.txt # look at old version of a.txt</pre> | |
| <p>Search for regressions:</p> | |
| <pre class="screen">$ git bisect start | |
| $ git bisect bad # current version is bad | |
| $ git bisect good v2.6.13-rc2 # last known good revision | |
| Bisecting: 675 revisions left to test after this | |
| # test here, then: | |
| $ git bisect good # if this revision is good, or | |
| $ git bisect bad # if this revision is bad. | |
| # repeat until done.</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="making-changes"></a>Making changes</h2></div></div></div> | |
| <p>Make sure Git knows who to blame:</p> | |
| <pre class="screen">$ cat >>~/.gitconfig <<\EOF | |
| [user] | |
| name = Your Name Comes Here | |
| email = you@yourdomain.example.com | |
| EOF</pre> | |
| <p>Select file contents to include in the next commit, then make the | |
| commit:</p> | |
| <pre class="screen">$ git add a.txt # updated file | |
| $ git add b.txt # new file | |
| $ git rm c.txt # old file | |
| $ git commit</pre> | |
| <p>Or, prepare and create the commit in one step:</p> | |
| <pre class="screen">$ git commit d.txt # use latest content only of d.txt | |
| $ git commit -a # use latest content of all tracked files</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="merging"></a>Merging</h2></div></div></div> | |
| <pre class="screen">$ git merge test # merge branch "test" into the current branch | |
| $ git pull git://example.com/project.git master | |
| # fetch and merge in remote branch | |
| $ git pull . test # equivalent to git merge test</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sharing-your-changes"></a>Sharing your changes</h2></div></div></div> | |
| <p>Importing or exporting patches:</p> | |
| <pre class="screen">$ git format-patch origin..HEAD # format a patch for each commit | |
| # in HEAD but not in origin | |
| $ git am mbox # import patches from the mailbox "mbox"</pre> | |
| <p>Fetch a branch in a different Git repository, then merge into the | |
| current branch:</p> | |
| <pre class="screen">$ git pull git://example.com/project.git theirbranch</pre> | |
| <p>Store the fetched branch into a local branch before merging into the | |
| current branch:</p> | |
| <pre class="screen">$ git pull git://example.com/project.git theirbranch:mybranch</pre> | |
| <p>After creating commits on a local branch, update the remote | |
| branch with your commits:</p> | |
| <pre class="screen">$ git push ssh://example.com/project.git mybranch:theirbranch</pre> | |
| <p>When remote and local branch are both named "test":</p> | |
| <pre class="screen">$ git push ssh://example.com/project.git test</pre> | |
| <p>Shortcut version for a frequently used remote repository:</p> | |
| <pre class="screen">$ git remote add example ssh://example.com/project.git | |
| $ git push example test</pre> | |
| </div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="repository-maintenance"></a>Repository maintenance</h2></div></div></div> | |
| <p>Check for corruption:</p> | |
| <pre class="screen">$ git fsck</pre> | |
| <p>Recompress, remove unused cruft:</p> | |
| <pre class="screen">$ git gc</pre> | |
| </div> | |
| </div> | |
| <div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a name="todo"></a>Appendix B. Notes and todo list for this manual</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#todo-list">Todo list</a></span></dt></dl></div> | |
| <div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="todo-list"></a>Todo list</h2></div></div></div> | |
| <p>This is a work in progress.</p> | |
| <p>The basic requirements:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| It must be readable in order, from beginning to end, by someone | |
| intelligent with a basic grasp of the UNIX command line, but without | |
| any special knowledge of Git. If necessary, any other prerequisites | |
| should be specifically mentioned as they arise. | |
| </li><li class="listitem"> | |
| Whenever possible, section headings should clearly describe the task | |
| they explain how to do, in language that requires no more knowledge | |
| than necessary: for example, "importing patches into a project" rather | |
| than "the <code class="literal">git</code> <code class="literal">am</code> command" | |
| </li></ul></div> | |
| <p>Think about how to create a clear chapter dependency graph that will | |
| allow people to get to important topics without necessarily reading | |
| everything in between.</p> | |
| <p>Scan <code class="literal">Documentation/</code> for other stuff left out; in particular:</p> | |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
| howto’s | |
| </li><li class="listitem"> | |
| some of <code class="literal">technical/</code>? | |
| </li><li class="listitem"> | |
| hooks | |
| </li><li class="listitem"> | |
| list of commands in <a class="ulink" href="git.html" target="_top">git(1)</a> | |
| </li></ul></div> | |
| <p>Scan email archives for other stuff left out</p> | |
| <p>Scan man pages to see if any assume more background than this manual | |
| provides.</p> | |
| <p>Add more good examples. Entire sections of just cookbook examples | |
| might be a good idea; maybe make an "advanced examples" section a | |
| standard end-of-chapter section?</p> | |
| <p>Include cross-references to the glossary, where appropriate.</p> | |
| <p>Add a section on working with other version control systems, including | |
| CVS, Subversion, and just imports of series of release tarballs.</p> | |
| <p>Write a chapter on using plumbing and writing scripts.</p> | |
| <p>Alternates, clone -reference, etc.</p> | |
| <p>More on recovery from repository corruption. See: | |
| <a class="ulink" href="https://lore.kernel.org/git/Pine.LNX.4.64.0702272039540.12485@woody.linux-foundation.org/" target="_top">https://lore.kernel.org/git/Pine.LNX.4.64.0702272039540.12485@woody.linux-foundation.org/</a> | |
| <a class="ulink" href="https://lore.kernel.org/git/Pine.LNX.4.64.0702141033400.3604@woody.linux-foundation.org/" target="_top">https://lore.kernel.org/git/Pine.LNX.4.64.0702141033400.3604@woody.linux-foundation.org/</a></p> | |
| </div> | |
| </div> | |
| </div></body></html> |