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<body class="article">
<div id="header">
<h1>merge API</h1>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="paragraph"><p>The merge API helps a program to reconcile two competing sets of
improvements to some files (e.g., unregistered changes from the work
tree versus changes involved in switching to a new branch), reporting
conflicts if found.  The library called through this API is
responsible for a few things.</p></div>
<div class="ulist"><ul>
<li>
<p>
determining which trees to merge (recursive ancestor consolidation);
</p>
</li>
<li>
<p>
lining up corresponding files in the trees to be merged (rename
   detection, subtree shifting), reporting edge cases like add/add
   and rename/rename conflicts to the user;
</p>
</li>
<li>
<p>
performing a three-way merge of corresponding files, taking
   path-specific merge drivers (specified in <code>.gitattributes</code>)
   into account.
</p>
</li>
</ul></div>
</div>
</div>
<div class="sect1">
<h2 id="_data_structures">Data structures</h2>
<div class="sectionbody">
<div class="ulist"><ul>
<li>
<p>
<code>mmbuffer_t</code>, <code>mmfile_t</code>
</p>
</li>
</ul></div>
<div class="paragraph"><p>These store data usable for use by the xdiff backend, for writing and
for reading, respectively.  See <code>xdiff/xdiff.h</code> for the definitions
and <code>diff.c</code> for examples.</p></div>
<div class="ulist"><ul>
<li>
<p>
<code>struct ll_merge_options</code>
</p>
</li>
</ul></div>
<div class="paragraph"><p>This describes the set of options the calling program wants to affect
the operation of a low-level (single file) merge.  Some options:</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<code>virtual_ancestor</code>
</dt>
<dd>
<p>
        Behave as though this were part of a merge between common
        ancestors in a recursive merge.
        If a helper program is specified by the
        <code>[merge "&lt;driver&gt;"] recursive</code> configuration, it will
        be used (see <a href="../gitattributes.html">gitattributes(5)</a>).
</p>
</dd>
<dt class="hdlist1">
<code>variant</code>
</dt>
<dd>
<p>
        Resolve local conflicts automatically in favor
        of one side or the other (as in <em>git merge-file</em>
        <code>--ours</code>/<code>--theirs</code>/<code>--union</code>).  Can be <code>0</code>,
        <code>XDL_MERGE_FAVOR_OURS</code>, <code>XDL_MERGE_FAVOR_THEIRS</code>, or
        <code>XDL_MERGE_FAVOR_UNION</code>.
</p>
</dd>
<dt class="hdlist1">
<code>renormalize</code>
</dt>
<dd>
<p>
        Resmudge and clean the "base", "theirs" and "ours" files
        before merging.  Use this when the merge is likely to have
        overlapped with a change in smudge/clean or end-of-line
        normalization rules.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_low_level_single_file_merge">Low-level (single file) merge</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
<code>ll_merge</code>
</dt>
<dd>
<p>
        Perform a three-way single-file merge in core.  This is
        a thin wrapper around <code>xdl_merge</code> that takes the path and
        any merge backend specified in <code>.gitattributes</code> or
        <code>.git/info/attributes</code> into account.  Returns 0 for a
        clean merge.
</p>
</dd>
</dl></div>
<div class="paragraph"><p>Calling sequence:</p></div>
<div class="ulist"><ul>
<li>
<p>
Prepare a <code>struct ll_merge_options</code> to record options.
  If you have no special requests, skip this and pass <code>NULL</code>
  as the <code>opts</code> parameter to use the default options.
</p>
</li>
<li>
<p>
Allocate an mmbuffer_t variable for the result.
</p>
</li>
<li>
<p>
Allocate and fill variables with the file&#8217;s original content
  and two modified versions (using <code>read_mmfile</code>, for example).
</p>
</li>
<li>
<p>
Call <code>ll_merge()</code>.
</p>
</li>
<li>
<p>
Read the merged content from <code>result_buf.ptr</code> and <code>result_buf.size</code>.
</p>
</li>
<li>
<p>
Release buffers when finished.  A simple
  <code>free(ancestor.ptr); free(ours.ptr); free(theirs.ptr);
  free(result_buf.ptr);</code> will do.
</p>
</li>
</ul></div>
<div class="paragraph"><p>If the modifications do not merge cleanly, <code>ll_merge</code> will return a
nonzero value and <code>result_buf</code> will generally include a description of
the conflict bracketed by markers such as the traditional <code>&lt;&lt;&lt;&lt;&lt;&lt;&lt;</code>
and <code>&gt;&gt;&gt;&gt;&gt;&gt;&gt;</code>.</p></div>
<div class="paragraph"><p>The <code>ancestor_label</code>, <code>our_label</code>, and <code>their_label</code> parameters are
used to label the different sides of a conflict if the merge driver
supports this.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_everything_else">Everything else</h2>
<div class="sectionbody">
<div class="paragraph"><p>Talk about &lt;merge-recursive.h&gt; and merge_file():</p></div>
<div class="ulist"><ul>
<li>
<p>
merge_trees() to merge with rename detection
</p>
</li>
<li>
<p>
merge_recursive() for ancestor consolidation
</p>
</li>
<li>
<p>
try_merge_command() for other strategies
</p>
</li>
<li>
<p>
conflict format
</p>
</li>
<li>
<p>
merge options
</p>
</li>
</ul></div>
<div class="paragraph"><p>(Daniel, Miklos, Stephan, JC)</p></div>
</div>
</div>
</div>
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Last updated 2013-06-10 20:01:55 UTC
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