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 553 <div id="header">
 554 <h1>merge API</h1>
 555 </div>
 556 <div id="content">
 557 <div id="preamble">
 558 <div class="sectionbody">
 559 <div class="paragraph"><p>The merge API helps a program to reconcile two competing sets of
 560 improvements to some files (e.g., unregistered changes from the work
 561 tree versus changes involved in switching to a new branch), reporting
 562 conflicts if found.  The library called through this API is
 563 responsible for a few things.</p></div>
 564 <div class="ulist"><ul>
 565 <li>
 566 <p>
 567 determining which trees to merge (recursive ancestor consolidation);
 568 </p>
 569 </li>
 570 <li>
 571 <p>
 572 lining up corresponding files in the trees to be merged (rename
 573    detection, subtree shifting), reporting edge cases like add/add
 574    and rename/rename conflicts to the user;
 575 </p>
 576 </li>
 577 <li>
 578 <p>
 579 performing a three-way merge of corresponding files, taking
 580    path-specific merge drivers (specified in <tt>.gitattributes</tt>)
 581    into account.
 582 </p>
 583 </li>
 584 </ul></div>
 585 </div>
 586 </div>
 587 <h2 id="_data_structures">Data structures</h2>
 588 <div class="sectionbody">
 589 <div class="ulist"><ul>
 590 <li>
 591 <p>
 592 <tt>mmbuffer_t</tt>, <tt>mmfile_t</tt>
 593 </p>
 594 </li>
 595 </ul></div>
 596 <div class="paragraph"><p>These store data usable for use by the xdiff backend, for writing and
 597 for reading, respectively.  See <tt>xdiff/xdiff.h</tt> for the definitions
 598 and <tt>diff.c</tt> for examples.</p></div>
 599 <div class="ulist"><ul>
 600 <li>
 601 <p>
 602 <tt>struct ll_merge_options</tt>
 603 </p>
 604 </li>
 605 </ul></div>
 606 <div class="paragraph"><p>This describes the set of options the calling program wants to affect
 607 the operation of a low-level (single file) merge.  Some options:</p></div>
 608 <div class="dlist"><dl>
 609 <dt class="hdlist1">
 610 <tt>virtual_ancestor</tt>
 611 </dt>
 612 <dd>
 613 <p>
 614         Behave as though this were part of a merge between common
 615         ancestors in a recursive merge.
 616         If a helper program is specified by the
 617         <tt>[merge "&lt;driver&gt;"] recursive</tt> configuration, it will
 618         be used (see <a href="gitattributes.html">gitattributes(5)</a>).
 619 </p>
 620 </dd>
 621 <dt class="hdlist1">
 622 <tt>variant</tt>
 623 </dt>
 624 <dd>
 625 <p>
 626         Resolve local conflicts automatically in favor
 627         of one side or the other (as in <em>git merge-file</em>
 628         <tt>--ours</tt>/<tt>--theirs</tt>/<tt>--union</tt>).  Can be <tt>0</tt>,
 629         <tt>XDL_MERGE_FAVOR_OURS</tt>, <tt>XDL_MERGE_FAVOR_THEIRS</tt>, or
 630         <tt>XDL_MERGE_FAVOR_UNION</tt>.
 631 </p>
 632 </dd>
 633 <dt class="hdlist1">
 634 <tt>renormalize</tt>
 635 </dt>
 636 <dd>
 637 <p>
 638         Resmudge and clean the "base", "theirs" and "ours" files
 639         before merging.  Use this when the merge is likely to have
 640         overlapped with a change in smudge/clean or end-of-line
 641         normalization rules.
 642 </p>
 643 </dd>
 644 </dl></div>
 645 </div>
 646 <h2 id="_low_level_single_file_merge">Low-level (single file) merge</h2>
 647 <div class="sectionbody">
 648 <div class="dlist"><dl>
 649 <dt class="hdlist1">
 650 <tt>ll_merge</tt>
 651 </dt>
 652 <dd>
 653 <p>
 654         Perform a three-way single-file merge in core.  This is
 655         a thin wrapper around <tt>xdl_merge</tt> that takes the path and
 656         any merge backend specified in <tt>.gitattributes</tt> or
 657         <tt>.git/info/attributes</tt> into account.  Returns 0 for a
 658         clean merge.
 659 </p>
 660 </dd>
 661 </dl></div>
 662 <div class="paragraph"><p>Calling sequence:</p></div>
 663 <div class="ulist"><ul>
 664 <li>
 665 <p>
 666 Prepare a <tt>struct ll_merge_options</tt> to record options.
 667   If you have no special requests, skip this and pass <tt>NULL</tt>
 668   as the <tt>opts</tt> parameter to use the default options.
 669 </p>
 670 </li>
 671 <li>
 672 <p>
 673 Allocate an mmbuffer_t variable for the result.
 674 </p>
 675 </li>
 676 <li>
 677 <p>
 678 Allocate and fill variables with the file&#8217;s original content
 679   and two modified versions (using <tt>read_mmfile</tt>, for example).
 680 </p>
 681 </li>
 682 <li>
 683 <p>
 684 Call <tt>ll_merge()</tt>.
 685 </p>
 686 </li>
 687 <li>
 688 <p>
 689 Read the merged content from <tt>result_buf.ptr</tt> and <tt>result_buf.size</tt>.
 690 </p>
 691 </li>
 692 <li>
 693 <p>
 694 Release buffers when finished.  A simple
 695   <tt>free(ancestor.ptr); free(ours.ptr); free(theirs.ptr);
 696   free(result_buf.ptr);</tt> will do.
 697 </p>
 698 </li>
 699 </ul></div>
 700 <div class="paragraph"><p>If the modifications do not merge cleanly, <tt>ll_merge</tt> will return a
 701 nonzero value and <tt>result_buf</tt> will generally include a description of
 702 the conflict bracketed by markers such as the traditional <tt>&lt;&lt;&lt;&lt;&lt;&lt;&lt;</tt>
 703 and <tt>&gt;&gt;&gt;&gt;&gt;&gt;&gt;</tt>.</p></div>
 704 <div class="paragraph"><p>The <tt>ancestor_label</tt>, <tt>our_label</tt>, and <tt>their_label</tt> parameters are
 705 used to label the different sides of a conflict if the merge driver
 706 supports this.</p></div>
 707 </div>
 708 <h2 id="_everything_else">Everything else</h2>
 709 <div class="sectionbody">
 710 <div class="paragraph"><p>Talk about &lt;merge-recursive.h&gt; and merge_file():</p></div>
 711 <div class="ulist"><ul>
 712 <li>
 713 <p>
 714 merge_trees() to merge with rename detection
 715 </p>
 716 </li>
 717 <li>
 718 <p>
 719 merge_recursive() for ancestor consolidation
 720 </p>
 721 </li>
 722 <li>
 723 <p>
 724 try_merge_command() for other strategies
 725 </p>
 726 </li>
 727 <li>
 728 <p>
 729 conflict format
 730 </p>
 731 </li>
 732 <li>
 733 <p>
 734 merge options
 735 </p>
 736 </li>
 737 </ul></div>
 738 <div class="paragraph"><p>(Daniel, Miklos, Stephan, JC)</p></div>
 739 </div>
 740 </div>
 741 <div id="footnotes"><hr /></div>
 742 <div id="footer">
 743 <div id="footer-text">
 744 Last updated 2011-09-21 23:01:14 PDT
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