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} div.exampleblock-content { border-left: 2px solid silver; padding-left: 0.5em; } /* IE6 sets dynamically generated links as visited. */ div#toc a:visited { color: blue; } </style> </head> <body> <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> <h2 id="_synopsis">SYNOPSIS</h2> <div class="sectionbody"> <div class="verseblock"> <div class="verseblock-content"><em>git merge-base</em> [-a|--all] [--octopus] <commit> <commit>… <em>git merge-base</em> --independent <commit>…</div> <div class="verseblock-attribution"> </div></div> </div> <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 class="paragraph"><p>Unless <tt>--octopus</tt> is given, 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. 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>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 <tt>--merge-base</tt> option.</p></div> </div> <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> <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> </dl></div> </div> <h2 id="_discussion">DISCUSSION</h2> <div class="sectionbody"> <div class="paragraph"><p>Given two commits <em>A</em> and <em>B</em>, <tt>git merge-base A B</tt> 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><tt> o---o---o---B / ---o---1---o---o---o---A</tt></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>, <tt>git merge-base A B C</tt> 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><tt> o---o---o---o---C / / o---o---o---B / / ---2---1---o---o---o---A</tt></pre> </div></div> <div class="paragraph"><p>the result of <tt>git merge-base A B C</tt> 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><tt> o---o---o---o---o / \ / o---o---o---o---M / / ---2---1---o---o---o---A</tt></pre> </div></div> <div class="paragraph"><p>and the result of <tt>git merge-base A M</tt> 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>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><tt>---1---o---A \ / X / \ ---2---o---o---B</tt></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 <tt>--all</tt> option is not given, it is unspecified which best one is output.</p></div> </div> <h2 id="_author">Author</h2> <div class="sectionbody"> <div class="paragraph"><p>Written by Linus Torvalds <<a href="mailto:torvalds@osdl.org">torvalds@osdl.org</a>></p></div> </div> <h2 id="_documentation">Documentation</h2> <div class="sectionbody"> <div class="paragraph"><p>Documentation by David Greaves, Junio C Hamano and the git-list <<a href="mailto:git@vger.kernel.org">git@vger.kernel.org</a>>.</p></div> </div> <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> <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 id="footer"> <div id="footer-text"> Last updated 2010-12-16 02:52:11 UTC </div> </div> </body> </html>