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<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 <tt>.gitattributes</tt>)
into account.
</p>
</li>
</ul></div>
</div>
</div>
<h2 id="_data_structures">Data structures</h2>
<div class="sectionbody">
<div class="ulist"><ul>
<li>
<p>
<tt>mmbuffer_t</tt>, <tt>mmfile_t</tt>
</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 <tt>xdiff/xdiff.h</tt> for the definitions
and <tt>diff.c</tt> for examples.</p></div>
<div class="ulist"><ul>
<li>
<p>
<tt>struct ll_merge_options</tt>
</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">
<tt>virtual_ancestor</tt>
</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
<tt>[merge "<driver>"] recursive</tt> configuration, it will
be used (see <a href="../gitattributes.html">gitattributes(5)</a>).
</p>
</dd>
<dt class="hdlist1">
<tt>variant</tt>
</dt>
<dd>
<p>
Resolve local conflicts automatically in favor
of one side or the other (as in <em>git merge-file</em>
<tt>--ours</tt>/<tt>--theirs</tt>/<tt>--union</tt>). Can be <tt>0</tt>,
<tt>XDL_MERGE_FAVOR_OURS</tt>, <tt>XDL_MERGE_FAVOR_THEIRS</tt>, or
<tt>XDL_MERGE_FAVOR_UNION</tt>.
</p>
</dd>
<dt class="hdlist1">
<tt>renormalize</tt>
</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>
<h2 id="_low_level_single_file_merge">Low-level (single file) merge</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
<tt>ll_merge</tt>
</dt>
<dd>
<p>
Perform a three-way single-file merge in core. This is
a thin wrapper around <tt>xdl_merge</tt> that takes the path and
any merge backend specified in <tt>.gitattributes</tt> or
<tt>.git/info/attributes</tt> 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 <tt>struct ll_merge_options</tt> to record options.
If you have no special requests, skip this and pass <tt>NULL</tt>
as the <tt>opts</tt> 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’s original content
and two modified versions (using <tt>read_mmfile</tt>, for example).
</p>
</li>
<li>
<p>
Call <tt>ll_merge()</tt>.
</p>
</li>
<li>
<p>
Read the merged content from <tt>result_buf.ptr</tt> and <tt>result_buf.size</tt>.
</p>
</li>
<li>
<p>
Release buffers when finished. A simple
<tt>free(ancestor.ptr); free(ours.ptr); free(theirs.ptr);
free(result_buf.ptr);</tt> will do.
</p>
</li>
</ul></div>
<div class="paragraph"><p>If the modifications do not merge cleanly, <tt>ll_merge</tt> will return a
nonzero value and <tt>result_buf</tt> will generally include a description of
the conflict bracketed by markers such as the traditional <tt><<<<<<<</tt>
and <tt>>>>>>>></tt>.</p></div>
<div class="paragraph"><p>The <tt>ancestor_label</tt>, <tt>our_label</tt>, and <tt>their_label</tt> parameters are
used to label the different sides of a conflict if the merge driver
supports this.</p></div>
</div>
<h2 id="_everything_else">Everything else</h2>
<div class="sectionbody">
<div class="paragraph"><p>Talk about <merge-recursive.h> 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 id="footnotes"><hr /></div>
<div id="footer">
<div id="footer-text">
Last updated 2012-06-08 11:37:18 PDT
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