| <?xml version="1.0" encoding="UTF-8"?> | |
| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" | |
| "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> | |
| <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> | |
| <head> | |
| <meta http-equiv="Content-Type" content="application/xhtml+xml; charset=UTF-8" /> | |
| <meta name="generator" content="AsciiDoc 8.6.10" /> | |
| <title>git-merge-base(1)</title> | |
| <style type="text/css"> | |
| /* Shared CSS for AsciiDoc xhtml11 and html5 backends */ | |
| /* Default font. */ | |
| body { | |
| font-family: Georgia,serif; | |
| } | |
| /* Title font. */ | |
| h1, h2, h3, h4, h5, h6, | |
| div.title, caption.title, | |
| thead, p.table.header, | |
| #toctitle, | |
| #author, #revnumber, #revdate, #revremark, | |
| #footer { | |
| font-family: Arial,Helvetica,sans-serif; | |
| } | |
| body { | |
| margin: 1em 5% 1em 5%; | |
| } | |
| a { | |
| color: blue; | |
| text-decoration: underline; | |
| } | |
| a:visited { | |
| color: fuchsia; | |
| } | |
| em { | |
| font-style: italic; | |
| color: navy; | |
| } | |
| strong { | |
| font-weight: bold; | |
| color: #083194; | |
| } | |
| h1, h2, h3, h4, h5, h6 { | |
| color: #527bbd; | |
| margin-top: 1.2em; | |
| margin-bottom: 0.5em; | |
| line-height: 1.3; | |
| } | |
| h1, h2, h3 { | |
| border-bottom: 2px solid silver; | |
| } | |
| h2 { | |
| padding-top: 0.5em; | |
| } | |
| h3 { | |
| float: left; | |
| } | |
| h3 + * { | |
| clear: left; | |
| } | |
| h5 { | |
| font-size: 1.0em; | |
| } | |
| div.sectionbody { | |
| margin-left: 0; | |
| } | |
| hr { | |
| border: 1px solid silver; | |
| } | |
| p { | |
| margin-top: 0.5em; | |
| margin-bottom: 0.5em; | |
| } | |
| ul, ol, li > p { | |
| margin-top: 0; | |
| } | |
| ul > li { color: #aaa; } | |
| ul > li > * { color: black; } | |
| .monospaced, code, pre { | |
| font-family: "Courier New", Courier, monospace; | |
| font-size: inherit; | |
| color: navy; | |
| padding: 0; | |
| margin: 0; | |
| } | |
| pre { | |
| white-space: pre-wrap; | |
| } | |
| #author { | |
| color: #527bbd; | |
| font-weight: bold; | |
| font-size: 1.1em; | |
| } | |
| #email { | |
| } | |
| #revnumber, #revdate, #revremark { | |
| } | |
| #footer { | |
| font-size: small; | |
| border-top: 2px solid silver; | |
| padding-top: 0.5em; | |
| margin-top: 4.0em; | |
| } | |
| #footer-text { | |
| float: left; | |
| padding-bottom: 0.5em; | |
| } | |
| #footer-badges { | |
| float: right; | |
| padding-bottom: 0.5em; | |
| } | |
| #preamble { | |
| margin-top: 1.5em; | |
| margin-bottom: 1.5em; | |
| } | |
| div.imageblock, div.exampleblock, div.verseblock, | |
| div.quoteblock, div.literalblock, div.listingblock, div.sidebarblock, | |
| div.admonitionblock { | |
| margin-top: 1.0em; | |
| margin-bottom: 1.5em; | |
| } | |
| div.admonitionblock { | |
| margin-top: 2.0em; | |
| margin-bottom: 2.0em; | |
| margin-right: 10%; | |
| color: #606060; | |
| } | |
| div.content { /* Block element content. */ | |
| padding: 0; | |
| } | |
| /* Block element titles. */ | |
| div.title, caption.title { | |
| color: #527bbd; | |
| font-weight: bold; | |
| text-align: left; | |
| margin-top: 1.0em; | |
| margin-bottom: 0.5em; | |
| } | |
| div.title + * { | |
| margin-top: 0; | |
| } | |
| td div.title:first-child { | |
| margin-top: 0.0em; | |
| } | |
| div.content div.title:first-child { | |
| margin-top: 0.0em; | |
| } | |
| div.content + div.title { | |
| margin-top: 0.0em; | |
| } | |
| div.sidebarblock > div.content { | |
| background: #ffffee; | |
| border: 1px solid #dddddd; | |
| border-left: 4px solid #f0f0f0; | |
| padding: 0.5em; | |
| } | |
| div.listingblock > div.content { | |
| border: 1px solid #dddddd; | |
| border-left: 5px solid #f0f0f0; | |
| background: #f8f8f8; | |
| padding: 0.5em; | |
| } | |
| div.quoteblock, div.verseblock { | |
| padding-left: 1.0em; | |
| margin-left: 1.0em; | |
| margin-right: 10%; | |
| border-left: 5px solid #f0f0f0; | |
| color: #888; | |
| } | |
| div.quoteblock > div.attribution { | |
| padding-top: 0.5em; | |
| text-align: right; | |
| } | |
| div.verseblock > pre.content { | |
| font-family: inherit; | |
| font-size: inherit; | |
| } | |
| div.verseblock > div.attribution { | |
| padding-top: 0.75em; | |
| text-align: left; | |
| } | |
| /* DEPRECATED: Pre version 8.2.7 verse style literal block. */ | |
| div.verseblock + div.attribution { | |
| text-align: left; | |
| } | |
| div.admonitionblock .icon { | |
| vertical-align: top; | |
| font-size: 1.1em; | |
| font-weight: bold; | |
| text-decoration: underline; | |
| color: #527bbd; | |
| padding-right: 0.5em; | |
| } | |
| div.admonitionblock td.content { | |
| padding-left: 0.5em; | |
| border-left: 3px solid #dddddd; | |
| } | |
| div.exampleblock > div.content { | |
| border-left: 3px solid #dddddd; | |
| padding-left: 0.5em; | |
| } | |
| div.imageblock div.content { padding-left: 0; } | |
| span.image img { border-style: none; vertical-align: text-bottom; } | |
| a.image:visited { color: white; } | |
| dl { | |
| margin-top: 0.8em; | |
| margin-bottom: 0.8em; | |
| } | |
| dt { | |
| margin-top: 0.5em; | |
| margin-bottom: 0; | |
| font-style: normal; | |
| color: navy; | |
| } | |
| dd > *:first-child { | |
| margin-top: 0.1em; | |
| } | |
| ul, ol { | |
| list-style-position: outside; | |
| } | |
| ol.arabic { | |
| list-style-type: decimal; | |
| } | |
| ol.loweralpha { | |
| list-style-type: lower-alpha; | |
| } | |
| ol.upperalpha { | |
| list-style-type: upper-alpha; | |
| } | |
| ol.lowerroman { | |
| list-style-type: lower-roman; | |
| } | |
| ol.upperroman { | |
| list-style-type: upper-roman; | |
| } | |
| div.compact ul, div.compact ol, | |
| div.compact p, div.compact p, | |
| div.compact div, div.compact div { | |
| margin-top: 0.1em; | |
| margin-bottom: 0.1em; | |
| } | |
| tfoot { | |
| font-weight: bold; | |
| } | |
| td > div.verse { | |
| white-space: pre; | |
| } | |
| div.hdlist { | |
| margin-top: 0.8em; | |
| margin-bottom: 0.8em; | |
| } | |
| div.hdlist tr { | |
| padding-bottom: 15px; | |
| } | |
| dt.hdlist1.strong, td.hdlist1.strong { | |
| font-weight: bold; | |
| } | |
| td.hdlist1 { | |
| vertical-align: top; | |
| font-style: normal; | |
| padding-right: 0.8em; | |
| color: navy; | |
| } | |
| td.hdlist2 { | |
| vertical-align: top; | |
| } | |
| div.hdlist.compact tr { | |
| margin: 0; | |
| padding-bottom: 0; | |
| } | |
| .comment { | |
| background: yellow; | |
| } | |
| .footnote, .footnoteref { | |
| font-size: 0.8em; | |
| } | |
| span.footnote, span.footnoteref { | |
| vertical-align: super; | |
| } | |
| #footnotes { | |
| margin: 20px 0 20px 0; | |
| padding: 7px 0 0 0; | |
| } | |
| #footnotes div.footnote { | |
| margin: 0 0 5px 0; | |
| } | |
| #footnotes hr { | |
| border: none; | |
| border-top: 1px solid silver; | |
| height: 1px; | |
| text-align: left; | |
| margin-left: 0; | |
| width: 20%; | |
| min-width: 100px; | |
| } | |
| div.colist td { | |
| padding-right: 0.5em; | |
| padding-bottom: 0.3em; | |
| vertical-align: top; | |
| } | |
| div.colist td img { | |
| margin-top: 0.3em; | |
| } | |
| @media print { | |
| #footer-badges { display: none; } | |
| } | |
| #toc { | |
| margin-bottom: 2.5em; | |
| } | |
| #toctitle { | |
| color: #527bbd; | |
| font-size: 1.1em; | |
| font-weight: bold; | |
| margin-top: 1.0em; | |
| margin-bottom: 0.1em; | |
| } | |
| div.toclevel0, div.toclevel1, div.toclevel2, div.toclevel3, div.toclevel4 { | |
| margin-top: 0; | |
| margin-bottom: 0; | |
| } | |
| div.toclevel2 { | |
| margin-left: 2em; | |
| font-size: 0.9em; | |
| } | |
| div.toclevel3 { | |
| margin-left: 4em; | |
| font-size: 0.9em; | |
| } | |
| div.toclevel4 { | |
| margin-left: 6em; | |
| font-size: 0.9em; | |
| } | |
| span.aqua { color: aqua; } | |
| span.black { color: black; } | |
| span.blue { color: blue; } | |
| span.fuchsia { color: fuchsia; } | |
| span.gray { color: gray; } | |
| span.green { color: green; } | |
| span.lime { color: lime; } | |
| span.maroon { color: maroon; } | |
| span.navy { color: navy; } | |
| span.olive { color: olive; } | |
| span.purple { color: purple; } | |
| span.red { color: red; } | |
| span.silver { color: silver; } | |
| span.teal { color: teal; } | |
| span.white { color: white; } | |
| span.yellow { color: yellow; } | |
| span.aqua-background { background: aqua; } | |
| span.black-background { background: black; } | |
| span.blue-background { background: blue; } | |
| span.fuchsia-background { background: fuchsia; } | |
| span.gray-background { background: gray; } | |
| span.green-background { background: green; } | |
| span.lime-background { background: lime; } | |
| span.maroon-background { background: maroon; } | |
| span.navy-background { background: navy; } | |
| span.olive-background { background: olive; } | |
| span.purple-background { background: purple; } | |
| span.red-background { background: red; } | |
| span.silver-background { background: silver; } | |
| span.teal-background { background: teal; } | |
| span.white-background { background: white; } | |
| span.yellow-background { background: yellow; } | |
| span.big { font-size: 2em; } | |
| span.small { font-size: 0.6em; } | |
| span.underline { text-decoration: underline; } | |
| span.overline { text-decoration: overline; } | |
| span.line-through { text-decoration: line-through; } | |
| div.unbreakable { page-break-inside: avoid; } | |
| /* | |
| * xhtml11 specific | |
| * | |
| * */ | |
| div.tableblock { | |
| margin-top: 1.0em; | |
| margin-bottom: 1.5em; | |
| } | |
| div.tableblock > table { | |
| border: 3px solid #527bbd; | |
| } | |
| thead, p.table.header { | |
| font-weight: bold; | |
| color: #527bbd; | |
| } | |
| p.table { | |
| margin-top: 0; | |
| } | |
| /* Because the table frame attribute is overriden by CSS in most browsers. */ | |
| div.tableblock > table[frame="void"] { | |
| border-style: none; | |
| } | |
| div.tableblock > table[frame="hsides"] { | |
| border-left-style: none; | |
| border-right-style: none; | |
| } | |
| div.tableblock > table[frame="vsides"] { | |
| border-top-style: none; | |
| border-bottom-style: none; | |
| } | |
| /* | |
| * html5 specific | |
| * | |
| * */ | |
| table.tableblock { | |
| margin-top: 1.0em; | |
| margin-bottom: 1.5em; | |
| } | |
| thead, p.tableblock.header { | |
| font-weight: bold; | |
| color: #527bbd; | |
| } | |
| p.tableblock { | |
| margin-top: 0; | |
| } | |
| table.tableblock { | |
| border-width: 3px; | |
| border-spacing: 0px; | |
| border-style: solid; | |
| border-color: #527bbd; | |
| border-collapse: collapse; | |
| } | |
| th.tableblock, td.tableblock { | |
| border-width: 1px; | |
| padding: 4px; | |
| border-style: solid; | |
| border-color: #527bbd; | |
| } | |
| table.tableblock.frame-topbot { | |
| border-left-style: hidden; | |
| border-right-style: hidden; | |
| } | |
| table.tableblock.frame-sides { | |
| border-top-style: hidden; | |
| border-bottom-style: hidden; | |
| } | |
| table.tableblock.frame-none { | |
| border-style: hidden; | |
| } | |
| th.tableblock.halign-left, td.tableblock.halign-left { | |
| text-align: left; | |
| } | |
| th.tableblock.halign-center, td.tableblock.halign-center { | |
| text-align: center; | |
| } | |
| th.tableblock.halign-right, td.tableblock.halign-right { | |
| text-align: right; | |
| } | |
| th.tableblock.valign-top, td.tableblock.valign-top { | |
| vertical-align: top; | |
| } | |
| th.tableblock.valign-middle, td.tableblock.valign-middle { | |
| vertical-align: middle; | |
| } | |
| th.tableblock.valign-bottom, td.tableblock.valign-bottom { | |
| vertical-align: bottom; | |
| } | |
| /* | |
| * manpage specific | |
| * | |
| * */ | |
| body.manpage h1 { | |
| padding-top: 0.5em; | |
| padding-bottom: 0.5em; | |
| border-top: 2px solid silver; | |
| border-bottom: 2px solid silver; | |
| } | |
| body.manpage h2 { | |
| border-style: none; | |
| } | |
| body.manpage div.sectionbody { | |
| margin-left: 3em; | |
| } | |
| @media print { | |
| body.manpage div#toc { display: none; } | |
| } | |
| </style> | |
| <script type="text/javascript"> | |
| /*<+'])'); | |
| // Function that scans the DOM tree for header elements (the DOM2 | |
| // nodeIterator API would be a better technique but not supported by all | |
| // browsers). | |
| var iterate = function (el) { | |
| for (var i = el.firstChild; i != null; i = i.nextSibling) { | |
| if (i.nodeType == 1 /* Node.ELEMENT_NODE */) { | |
| var mo = re.exec(i.tagName); | |
| if (mo && (i.getAttribute("class") || i.getAttribute("className")) != "float") { | |
| result[result.length] = new TocEntry(i, getText(i), mo[1]-1); | |
| } | |
| iterate(i); | |
| } | |
| } | |
| } | |
| iterate(el); | |
| return result; | |
| } | |
| var toc = document.getElementById("toc"); | |
| if (!toc) { | |
| return; | |
| } | |
| // Delete existing TOC entries in case we're reloading the TOC. | |
| var tocEntriesToRemove = []; | |
| var i; | |
| for (i = 0; i < toc.childNodes.length; i++) { | |
| var entry = toc.childNodes[i]; | |
| if (entry.nodeName.toLowerCase() == 'div' | |
| && entry.getAttribute("class") | |
| && entry.getAttribute("class").match(/^toclevel/)) | |
| tocEntriesToRemove.push(entry); | |
| } | |
| for (i = 0; i < tocEntriesToRemove.length; i++) { | |
| toc.removeChild(tocEntriesToRemove[i]); | |
| } | |
| // Rebuild TOC entries. | |
| var entries = tocEntries(document.getElementById("content"), toclevels); | |
| for (var i = 0; i < entries.length; ++i) { | |
| var entry = entries[i]; | |
| if (entry.element.id == "") | |
| entry.element.id = "_toc_" + i; | |
| var a = document.createElement("a"); | |
| a.href = "#" + entry.element.id; | |
| a.appendChild(document.createTextNode(entry.text)); | |
| var div = document.createElement("div"); | |
| div.appendChild(a); | |
| div.className = "toclevel" + entry.toclevel; | |
| toc.appendChild(div); | |
| } | |
| if (entries.length == 0) | |
| toc.parentNode.removeChild(toc); | |
| }, | |
| ///////////////////////////////////////////////////////////////////// | |
| // Footnotes generator | |
| ///////////////////////////////////////////////////////////////////// | |
| /* Based on footnote generation code from: | |
| * http://www.brandspankingnew.net/archive/2005/07/format_footnote.html | |
| */ | |
| footnotes: function () { | |
| // Delete existing footnote entries in case we're reloading the footnodes. | |
| var i; | |
| var noteholder = document.getElementById("footnotes"); | |
| if (!noteholder) { | |
| return; | |
| } | |
| var entriesToRemove = []; | |
| for (i = 0; i < noteholder.childNodes.length; i++) { | |
| var entry = noteholder.childNodes[i]; | |
| if (entry.nodeName.toLowerCase() == 'div' && entry.getAttribute("class") == "footnote") | |
| entriesToRemove.push(entry); | |
| } | |
| for (i = 0; i < entriesToRemove.length; i++) { | |
| noteholder.removeChild(entriesToRemove[i]); | |
| } | |
| // Rebuild footnote entries. | |
| var cont = document.getElementById("content"); | |
| var spans = cont.getElementsByTagName("span"); | |
| var refs = {}; | |
| var n = 0; | |
| for (i=0; i<spans.length; i++) { | |
| if (spans[i].className == "footnote") { | |
| n++; | |
| var note = spans[i].getAttribute("data-note"); | |
| if (!note) { | |
| // Use [\s\S] in place of . so multi-line matches work. | |
| // Because JavaScript has no s (dotall) regex flag. | |
| note = spans[i].innerHTML.match(/\s*\[([\s\S]*)]\s*/)[1]; | |
| spans[i].innerHTML = | |
| "[<a id='_footnoteref_" + n + "' href='#_footnote_" + n + | |
| "' title='View footnote' class='footnote'>" + n + "</a>]"; | |
| spans[i].setAttribute("data-note", note); | |
| } | |
| noteholder.innerHTML += | |
| "<div class='footnote' id='_footnote_" + n + "'>" + | |
| "<a href='#_footnoteref_" + n + "' title='Return to text'>" + | |
| n + "</a>. " + note + "</div>"; | |
| var id =spans[i].getAttribute("id"); | |
| if (id != null) refs["#"+id] = n; | |
| } | |
| } | |
| if (n == 0) | |
| noteholder.parentNode.removeChild(noteholder); | |
| else { | |
| // Process footnoterefs. | |
| for (i=0; i<spans.length; i++) { | |
| if (spans[i].className == "footnoteref") { | |
| var href = spans[i].getElementsByTagName("a")[0].getAttribute("href"); | |
| href = href.match(/#.*/)[0]; // Because IE return full URL. | |
| n = refs[href]; | |
| spans[i].innerHTML = | |
| "[<a href='#_footnote_" + n + | |
| "' title='View footnote' class='footnote'>" + n + "</a>]"; | |
| } | |
| } | |
| } | |
| }, | |
| install: function(toclevels) { | |
| var timerId; | |
| function reinstall() { | |
| asciidoc.footnotes(); | |
| if (toclevels) { | |
| asciidoc.toc(toclevels); | |
| } | |
| } | |
| function reinstallAndRemoveTimer() { | |
| clearInterval(timerId); | |
| reinstall(); | |
| } | |
| timerId = setInterval(reinstall, 500); | |
| if (document.addEventListener) | |
| document.addEventListener("DOMContentLoaded", reinstallAndRemoveTimer, false); | |
| else | |
| window.onload = reinstallAndRemoveTimer; | |
| } | |
| } | |
| asciidoc.install(); | |
| /*]]>*/ | |
| </script> | |
| </head> | |
| <body class="manpage"> | |
| <div id="header"> | |
| <h1> | |
| git-merge-base(1) Manual Page | |
| </h1> | |
| <h2>NAME</h2> | |
| <div class="sectionbody"> | |
| <p>git-merge-base - | |
| Find as good common ancestors as possible for a merge | |
| </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 merge-base</em> [-a|--all] <commit> <commit>… | |
| <em>git merge-base</em> [-a|--all] --octopus <commit>… | |
| <em>git merge-base</em> --is-ancestor <commit> <commit> | |
| <em>git merge-base</em> --independent <commit>… | |
| <em>git merge-base</em> --fork-point <ref> [<commit>]</pre> | |
| <div class="attribution"> | |
| </div></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_description">DESCRIPTION</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p><em>git merge-base</em> finds best common ancestor(s) between two commits to use | |
| in a three-way merge. One common ancestor is <em>better</em> than another common | |
| ancestor if the latter is an ancestor of the former. A common ancestor | |
| that does not have any better common ancestor is a <em>best common | |
| ancestor</em>, i.e. a <em>merge base</em>. Note that there can be more than one | |
| merge base for a pair of commits.</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_operation_modes">OPERATION MODES</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>As the most common special case, specifying only two commits on the | |
| command line means computing the merge base between the given two commits.</p></div> | |
| <div class="paragraph"><p>More generally, among the two commits to compute the merge base from, | |
| one is specified by the first commit argument on the command line; | |
| the other commit is a (possibly hypothetical) commit that is a merge | |
| across all the remaining commits on the command line.</p></div> | |
| <div class="paragraph"><p>As a consequence, the <em>merge base</em> is not necessarily contained in each of the | |
| commit arguments if more than two commits are specified. This is different | |
| from <a href="git-show-branch.html">git-show-branch(1)</a> when used with the <code>--merge-base</code> option.</p></div> | |
| <div class="dlist"><dl> | |
| <dt class="hdlist1"> | |
| --octopus | |
| </dt> | |
| <dd> | |
| <p> | |
| Compute the best common ancestors of all supplied commits, | |
| in preparation for an n-way merge. This mimics the behavior | |
| of <em>git show-branch --merge-base</em>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| --independent | |
| </dt> | |
| <dd> | |
| <p> | |
| Instead of printing merge bases, print a minimal subset of | |
| the supplied commits with the same ancestors. In other words, | |
| among the commits given, list those which cannot be reached | |
| from any other. This mimics the behavior of <em>git show-branch | |
| --independent</em>. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| --is-ancestor | |
| </dt> | |
| <dd> | |
| <p> | |
| Check if the first <commit> is an ancestor of the second <commit>, | |
| and exit with status 0 if true, or with status 1 if not. | |
| Errors are signaled by a non-zero status that is not 1. | |
| </p> | |
| </dd> | |
| <dt class="hdlist1"> | |
| --fork-point | |
| </dt> | |
| <dd> | |
| <p> | |
| Find the point at which a branch (or any history that leads | |
| to <commit>) forked from another branch (or any reference) | |
| <ref>. This does not just look for the common ancestor of | |
| the two commits, but also takes into account the reflog of | |
| <ref> to see if the history leading to <commit> forked from | |
| an earlier incarnation of the branch <ref> (see discussion | |
| on this mode below). | |
| </p> | |
| </dd> | |
| </dl></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_options">OPTIONS</h2> | |
| <div class="sectionbody"> | |
| <div class="dlist"><dl> | |
| <dt class="hdlist1"> | |
| -a | |
| </dt> | |
| <dt class="hdlist1"> | |
| --all | |
| </dt> | |
| <dd> | |
| <p> | |
| Output all merge bases for the commits, instead of just one. | |
| </p> | |
| </dd> | |
| </dl></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_discussion">DISCUSSION</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>Given two commits <em>A</em> and <em>B</em>, <code>git merge-base A B</code> will output a commit | |
| which is reachable from both <em>A</em> and <em>B</em> through the parent relationship.</p></div> | |
| <div class="paragraph"><p>For example, with this topology:</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code> o---o---o---B | |
| / | |
| ---o---1---o---o---o---A</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>the merge base between <em>A</em> and <em>B</em> is <em>1</em>.</p></div> | |
| <div class="paragraph"><p>Given three commits <em>A</em>, <em>B</em> and <em>C</em>, <code>git merge-base A B C</code> will compute the | |
| merge base between <em>A</em> and a hypothetical commit <em>M</em>, which is a merge | |
| between <em>B</em> and <em>C</em>. For example, with this topology:</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code> o---o---o---o---C | |
| / | |
| / o---o---o---B | |
| / / | |
| ---2---1---o---o---o---A</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>the result of <code>git merge-base A B C</code> is <em>1</em>. This is because the | |
| equivalent topology with a merge commit <em>M</em> between <em>B</em> and <em>C</em> is:</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code> o---o---o---o---o | |
| / \ | |
| / o---o---o---o---M | |
| / / | |
| ---2---1---o---o---o---A</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>and the result of <code>git merge-base A M</code> is <em>1</em>. Commit <em>2</em> is also a | |
| common ancestor between <em>A</em> and <em>M</em>, but <em>1</em> is a better common ancestor, | |
| because <em>2</em> is an ancestor of <em>1</em>. Hence, <em>2</em> is not a merge base.</p></div> | |
| <div class="paragraph"><p>The result of <code>git merge-base --octopus A B C</code> is <em>2</em>, because <em>2</em> is | |
| the best common ancestor of all commits.</p></div> | |
| <div class="paragraph"><p>When the history involves criss-cross merges, there can be more than one | |
| <em>best</em> common ancestor for two commits. For example, with this topology:</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code>---1---o---A | |
| \ / | |
| X | |
| / \ | |
| ---2---o---o---B</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>both <em>1</em> and <em>2</em> are merge-bases of A and B. Neither one is better than | |
| the other (both are <em>best</em> merge bases). When the <code>--all</code> option is not given, | |
| it is unspecified which best one is output.</p></div> | |
| <div class="paragraph"><p>A common idiom to check "fast-forward-ness" between two commits A | |
| and B is (or at least used to be) to compute the merge base between | |
| A and B, and check if it is the same as A, in which case, A is an | |
| ancestor of B. You will see this idiom used often in older scripts.</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code>A=$(git rev-parse --verify A) | |
| if test "$A" = "$(git merge-base A B)" | |
| then | |
| ... A is an ancestor of B ... | |
| fi</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>In modern git, you can say this in a more direct way:</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code>if git merge-base --is-ancestor A B | |
| then | |
| ... A is an ancestor of B ... | |
| fi</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>instead.</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_discussion_on_fork_point_mode">Discussion on fork-point mode</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p>After working on the <code>topic</code> branch created with <code>git checkout -b | |
| topic origin/master</code>, the history of remote-tracking branch | |
| <code>origin/master</code> may have been rewound and rebuilt, leading to a | |
| history of this shape:</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code> o---B2 | |
| / | |
| ---o---o---B1--o---o---o---B (origin/master) | |
| \ | |
| B0 | |
| \ | |
| D0---D1---D (topic)</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>where <code>origin/master</code> used to point at commits B0, B1, B2 and now it | |
| points at B, and your <code>topic</code> branch was started on top of it back | |
| when <code>origin/master</code> was at B0, and you built three commits, D0, D1, | |
| and D, on top of it. Imagine that you now want to rebase the work | |
| you did on the topic on top of the updated origin/master.</p></div> | |
| <div class="paragraph"><p>In such a case, <code>git merge-base origin/master topic</code> would return the | |
| parent of B0 in the above picture, but B0^..D is <strong>not</strong> the range of | |
| commits you would want to replay on top of B (it includes B0, which | |
| is not what you wrote; it is a commit the other side discarded when | |
| it moved its tip from B0 to B1).</p></div> | |
| <div class="paragraph"><p><code>git merge-base --fork-point origin/master topic</code> is designed to | |
| help in such a case. It takes not only B but also B0, B1, and B2 | |
| (i.e. old tips of the remote-tracking branches your repository’s | |
| reflog knows about) into account to see on which commit your topic | |
| branch was built and finds B0, allowing you to replay only the | |
| commits on your topic, excluding the commits the other side later | |
| discarded.</p></div> | |
| <div class="paragraph"><p>Hence</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code>$ fork_point=$(git merge-base --fork-point origin/master topic)</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>will find B0, and</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code>$ git rebase --onto origin/master $fork_point topic</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>will replay D0, D1 and D on top of B to create a new history of this | |
| shape:</p></div> | |
| <div class="literalblock"> | |
| <div class="content"> | |
| <pre><code> o---B2 | |
| / | |
| ---o---o---B1--o---o---o---B (origin/master) | |
| \ \ | |
| B0 D0'--D1'--D' (topic - updated) | |
| \ | |
| D0---D1---D (topic - old)</code></pre> | |
| </div></div> | |
| <div class="paragraph"><p>A caveat is that older reflog entries in your repository may be | |
| expired by <code>git gc</code>. If B0 no longer appears in the reflog of the | |
| remote-tracking branch <code>origin/master</code>, the <code>--fork-point</code> mode | |
| obviously cannot find it and fails, avoiding to give a random and | |
| useless result (such as the parent of B0, like the same command | |
| without the <code>--fork-point</code> option gives).</p></div> | |
| <div class="paragraph"><p>Also, the remote-tracking branch you use the <code>--fork-point</code> mode | |
| with must be the one your topic forked from its tip. If you forked | |
| from an older commit than the tip, this mode would not find the fork | |
| point (imagine in the above sample history B0 did not exist, | |
| origin/master started at B1, moved to B2 and then B, and you forked | |
| your topic at origin/master^ when origin/master was B1; the shape of | |
| the history would be the same as above, without B0, and the parent | |
| of B1 is what <code>git merge-base origin/master topic</code> correctly finds, | |
| but the <code>--fork-point</code> mode will not, because it is not one of the | |
| commits that used to be at the tip of origin/master).</p></div> | |
| </div> | |
| </div> | |
| <div class="sect1"> | |
| <h2 id="_see_also">See also</h2> | |
| <div class="sectionbody"> | |
| <div class="paragraph"><p><a href="git-rev-list.html">git-rev-list(1)</a>, | |
| <a href="git-show-branch.html">git-show-branch(1)</a>, | |
| <a href="git-merge.html">git-merge(1)</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 | |
| 2018-10-30 16:33:48 JST | |
| </div> | |
| </div> | |
| </body> | |
| </html> |