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| ///////////////////////////////////////////////////////////////////// | |
| // Footnotes generator | |
| ///////////////////////////////////////////////////////////////////// | |
| /* Based on footnote generation code from: | |
| * http://www.brandspankingnew.net/archive/2005/07/format_footnote.html | |
| */ | |
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| }, | |
| install: function(toclevels) { | |
| var timerId; | |
| function reinstall() { | |
| asciidoc.footnotes(); | |
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| } | |
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| asciidoc.install(); | |
| /*]]>*/ | |
| </script> | |
| </head> | |
| <body class="manpage"> | |
| <div id="header"> | |
| <h1> | |
| gitdiffcore(7) Manual Page | |
| </h1> | |
| <h2>NAME</h2> | |
| <div class="sectionbody"> | |
| <p>gitdiffcore - | |
| Tweaking diff output | |
| </p> | |
| </div> | |
| </div> | |
| <div id="content"> | |
| <div class="sect1"> | |
| <h2 id="_synopsis">SYNOPSIS</h2> | |
| <div class="sectionbody"> | |
| <div class="verseblock"> | |
| <pre class="content"><em>git diff</em> *</pre> | |
| <div class="attribution"> | |
| </div></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_description">DESCRIPTION</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>The diff commands <em>git diff-index</em>, <em>git diff-files</em>, and <em>git diff-tree</em> | |
| can be told to manipulate differences they find in | |
| unconventional ways before showing <em>diff</em> output. The manipulation | |
| is collectively called "diffcore transformation". This short note | |
| describes what they are and how to use them to produce <em>diff</em> output | |
| that is easier to understand than the conventional kind.</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_the_chain_of_operation">The chain of operation</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>The <em>git diff-*</em> family works by first comparing two sets of | |
| files:</p></div> | |
| <div class="ulist"><ul> | |
| <li> | |
| <p> | |
| <em>git diff-index</em> compares contents of a "tree" object and the | |
| working directory (when <code>--cached</code> flag is not used) or a | |
| "tree" object and the index file (when <code>--cached</code> flag is | |
| used); | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| <em>git diff-files</em> compares contents of the index file and the | |
| working directory; | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| <em>git diff-tree</em> compares contents of two "tree" objects; | |
| </p> | |
| </li> | |
| </ul></div> | |
| <div class="paragraph"><p>In all of these cases, the commands themselves first optionally limit | |
| the two sets of files by any pathspecs given on their command-lines, | |
| and compare corresponding paths in the two resulting sets of files.</p></div> | |
| <div class="paragraph"><p>The pathspecs are used to limit the world diff operates in. They remove | |
| the filepairs outside the specified sets of pathnames. E.g. If the | |
| input set of filepairs included:</p></div> | |
| <div class="listingblock"> | |
| <div class="content"> | |
| <pre><code>:100644 100644 bcd1234... 0123456... M junkfile</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>but the command invocation was <code>git diff-files myfile</code>, then the | |
| junkfile entry would be removed from the list because only "myfile" | |
| is under consideration.</p></div> | |
| <div class="paragraph"><p>The result of comparison is passed from these commands to what is | |
| internally called "diffcore", in a format similar to what is output | |
| when the -p option is not used. E.g.</p></div> | |
| <div class="listingblock"> | |
| <div class="content"> | |
| <pre><code>in-place edit :100644 100644 bcd1234... 0123456... M file0 | |
| create :000000 100644 0000000... 1234567... A file4 | |
| delete :100644 000000 1234567... 0000000... D file5 | |
| unmerged :000000 000000 0000000... 0000000... U file6</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>The diffcore mechanism is fed a list of such comparison results | |
| (each of which is called "filepair", although at this point each | |
| of them talks about a single file), and transforms such a list | |
| into another list. There are currently 5 such transformations:</p></div> | |
| <div class="ulist"><ul> | |
| <li> | |
| <p> | |
| diffcore-break | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| diffcore-rename | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| diffcore-merge-broken | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| diffcore-pickaxe | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| diffcore-order | |
| </p> | |
| </li> | |
| </ul></div> | |
| <div class="paragraph"><p>These are applied in sequence. The set of filepairs <em>git diff-*</em> | |
| commands find are used as the input to diffcore-break, and | |
| the output from diffcore-break is used as the input to the | |
| next transformation. The final result is then passed to the | |
| output routine and generates either diff-raw format (see Output | |
| format sections of the manual for <em>git diff-*</em> commands) or | |
| diff-patch format.</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_diffcore_break_for_splitting_up_complete_rewrites">diffcore-break: For Splitting Up Complete Rewrites</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>The second transformation in the chain is diffcore-break, and is | |
| controlled by the -B option to the <em>git diff-*</em> commands. This is | |
| used to detect a filepair that represents "complete rewrite" and | |
| break such filepair into two filepairs that represent delete and | |
| create. E.g. If the input contained this filepair:</p></div> | |
| <div class="listingblock"> | |
| <div class="content"> | |
| <pre><code>:100644 100644 bcd1234... 0123456... M file0</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>and if it detects that the file "file0" is completely rewritten, | |
| it changes it to:</p></div> | |
| <div class="listingblock"> | |
| <div class="content"> | |
| <pre><code>:100644 000000 bcd1234... 0000000... D file0 | |
| :000000 100644 0000000... 0123456... A file0</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>For the purpose of breaking a filepair, diffcore-break examines | |
| the extent of changes between the contents of the files before | |
| and after modification (i.e. the contents that have "bcd1234…" | |
| and "0123456…" as their SHA-1 content ID, in the above | |
| example). The amount of deletion of original contents and | |
| insertion of new material are added together, and if it exceeds | |
| the "break score", the filepair is broken into two. The break | |
| score defaults to 50% of the size of the smaller of the original | |
| and the result (i.e. if the edit shrinks the file, the size of | |
| the result is used; if the edit lengthens the file, the size of | |
| the original is used), and can be customized by giving a number | |
| after "-B" option (e.g. "-B75" to tell it to use 75%).</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_diffcore_rename_for_detecting_renames_and_copies">diffcore-rename: For Detecting Renames and Copies</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>This transformation is used to detect renames and copies, and is | |
| controlled by the -M option (to detect renames) and the -C option | |
| (to detect copies as well) to the <em>git diff-*</em> commands. If the | |
| input contained these filepairs:</p></div> | |
| <div class="listingblock"> | |
| <div class="content"> | |
| <pre><code>:100644 000000 0123456... 0000000... D fileX | |
| :000000 100644 0000000... 0123456... A file0</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>and the contents of the deleted file fileX is similar enough to | |
| the contents of the created file file0, then rename detection | |
| merges these filepairs and creates:</p></div> | |
| <div class="listingblock"> | |
| <div class="content"> | |
| <pre><code>:100644 100644 0123456... 0123456... R100 fileX file0</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>When the "-C" option is used, the original contents of modified files, | |
| and deleted files (and also unmodified files, if the | |
| "--find-copies-harder" option is used) are considered as candidates | |
| of the source files in rename/copy operation. If the input were like | |
| these filepairs, that talk about a modified file fileY and a newly | |
| created file file0:</p></div> | |
| <div class="listingblock"> | |
| <div class="content"> | |
| <pre><code>:100644 100644 0123456... 1234567... M fileY | |
| :000000 100644 0000000... bcd3456... A file0</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>the original contents of fileY and the resulting contents of | |
| file0 are compared, and if they are similar enough, they are | |
| changed to:</p></div> | |
| <div class="listingblock"> | |
| <div class="content"> | |
| <pre><code>:100644 100644 0123456... 1234567... M fileY | |
| :100644 100644 0123456... bcd3456... C100 fileY file0</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>In both rename and copy detection, the same "extent of changes" | |
| algorithm used in diffcore-break is used to determine if two | |
| files are "similar enough", and can be customized to use | |
| a similarity score different from the default of 50% by giving a | |
| number after the "-M" or "-C" option (e.g. "-M8" to tell it to use | |
| 8/10 = 80%).</p></div> | |
| <div class="paragraph"><p>Note. When the "-C" option is used with <code>--find-copies-harder</code> | |
| option, <em>git diff-*</em> commands feed unmodified filepairs to | |
| diffcore mechanism as well as modified ones. This lets the copy | |
| detector consider unmodified files as copy source candidates at | |
| the expense of making it slower. Without <code>--find-copies-harder</code>, | |
| <em>git diff-*</em> commands can detect copies only if the file that was | |
| copied happened to have been modified in the same changeset.</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_diffcore_merge_broken_for_putting_complete_rewrites_back_together">diffcore-merge-broken: For Putting Complete Rewrites Back Together</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>This transformation is used to merge filepairs broken by | |
| diffcore-break, and not transformed into rename/copy by | |
| diffcore-rename, back into a single modification. This always | |
| runs when diffcore-break is used.</p></div> | |
| <div class="paragraph"><p>For the purpose of merging broken filepairs back, it uses a | |
| different "extent of changes" computation from the ones used by | |
| diffcore-break and diffcore-rename. It counts only the deletion | |
| from the original, and does not count insertion. If you removed | |
| only 10 lines from a 100-line document, even if you added 910 | |
| new lines to make a new 1000-line document, you did not do a | |
| complete rewrite. diffcore-break breaks such a case in order to | |
| help diffcore-rename to consider such filepairs as candidate of | |
| rename/copy detection, but if filepairs broken that way were not | |
| matched with other filepairs to create rename/copy, then this | |
| transformation merges them back into the original | |
| "modification".</p></div> | |
| <div class="paragraph"><p>The "extent of changes" parameter can be tweaked from the | |
| default 80% (that is, unless more than 80% of the original | |
| material is deleted, the broken pairs are merged back into a | |
| single modification) by giving a second number to -B option, | |
| like these:</p></div> | |
| <div class="ulist"><ul> | |
| <li> | |
| <p> | |
| -B50/60 (give 50% "break score" to diffcore-break, use 60% | |
| for diffcore-merge-broken). | |
| </p> | |
| </li> | |
| <li> | |
| <p> | |
| -B/60 (the same as above, since diffcore-break defaults to 50%). | |
| </p> | |
| </li> | |
| </ul></div> | |
| <div class="paragraph"><p>Note that earlier implementation left a broken pair as a separate | |
| creation and deletion patches. This was an unnecessary hack and | |
| the latest implementation always merges all the broken pairs | |
| back into modifications, but the resulting patch output is | |
| formatted differently for easier review in case of such | |
| a complete rewrite by showing the entire contents of old version | |
| prefixed with <em>-</em>, followed by the entire contents of new | |
| version prefixed with <em>+</em>.</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_diffcore_pickaxe_for_detecting_addition_deletion_of_specified_string">diffcore-pickaxe: For Detecting Addition/Deletion of Specified String</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>This transformation limits the set of filepairs to those that change | |
| specified strings between the preimage and the postimage in a certain | |
| way. -S<block of text> and -G<regular expression> options are used to | |
| specify different ways these strings are sought.</p></div> | |
| <div class="paragraph"><p>"-S<block of text>" detects filepairs whose preimage and postimage | |
| have different number of occurrences of the specified block of text. | |
| By definition, it will not detect in-file moves. Also, when a | |
| changeset moves a file wholesale without affecting the interesting | |
| string, diffcore-rename kicks in as usual, and <code>-S</code> omits the filepair | |
| (since the number of occurrences of that string didn’t change in that | |
| rename-detected filepair). When used with <code>--pickaxe-regex</code>, treat | |
| the <block of text> as an extended POSIX regular expression to match, | |
| instead of a literal string.</p></div> | |
| <div class="paragraph"><p>"-G<regular expression>" (mnemonic: grep) detects filepairs whose | |
| textual diff has an added or a deleted line that matches the given | |
| regular expression. This means that it will detect in-file (or what | |
| rename-detection considers the same file) moves, which is noise. The | |
| implementation runs diff twice and greps, and this can be quite | |
| expensive.</p></div> | |
| <div class="paragraph"><p>When <code>-S</code> or <code>-G</code> are used without <code>--pickaxe-all</code>, only filepairs | |
| that match their respective criterion are kept in the output. When | |
| <code>--pickaxe-all</code> is used, if even one filepair matches their respective | |
| criterion in a changeset, the entire changeset is kept. This behavior | |
| is designed to make reviewing changes in the context of the whole | |
| changeset easier.</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_diffcore_order_for_sorting_the_output_based_on_filenames">diffcore-order: For Sorting the Output Based on Filenames</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>This is used to reorder the filepairs according to the user’s | |
| (or project’s) taste, and is controlled by the -O option to the | |
| <em>git diff-*</em> commands.</p></div> | |
| <div class="paragraph"><p>This takes a text file each of whose lines is a shell glob | |
| pattern. Filepairs that match a glob pattern on an earlier line | |
| in the file are output before ones that match a later line, and | |
| filepairs that do not match any glob pattern are output last.</p></div> | |
| <div class="paragraph"><p>As an example, a typical orderfile for the core Git probably | |
| would look like this:</p></div> | |
| <div class="listingblock"> | |
| <div class="content"> | |
| <pre><code>README | |
| Makefile | |
| Documentation | |
| *.h | |
| *.c | |
| t</code></pre> | |
| </div></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_see_also">SEE ALSO</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p><a href="git-diff.html">git-diff(1)</a>, | |
| <a href="git-diff-files.html">git-diff-files(1)</a>, | |
| <a href="git-diff-index.html">git-diff-index(1)</a>, | |
| <a href="git-diff-tree.html">git-diff-tree(1)</a>, | |
| <a href="git-format-patch.html">git-format-patch(1)</a>, | |
| <a href="git-log.html">git-log(1)</a>, | |
| <a href="gitglossary.html">gitglossary(7)</a>, | |
| <a href="user-manual.html">The Git User’s Manual</a></p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_git">GIT</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>Part of the <a href="git.html">git(1)</a> suite</p></div> | |
| </div> | |
| </div> | |
| </div> | |
| <div id="footnotes"><hr /></div> | |
| <div id="footer"> | |
| <div id="footer-text"> | |
| Last updated | |
| 2018-01-27 08:11:04 JST | |
| </div> | |
| </div> | |
| </body> | |
| </html> |