technical/api-builtin.html

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 552 <body>
 553 <div id="header">
 554 <h1>builtin API</h1>
 555 </div>
 556 <div id="content">
 557 <h2 id="_adding_a_new_built_in">Adding a new built-in</h2>
 558 <div class="sectionbody">
 559 <div class="paragraph"><p>There are 4 things to do to add a built-in command implementation to
 560 git:</p></div>
 561 <div class="olist arabic"><ol class="arabic">
 562 <li>
 563 <p>
 564 Define the implementation of the built-in command <tt>foo</tt> with
 565   signature:
 566 </p>
 567 <div class="literalblock">
 568 <div class="content">
 569 <pre><tt>int cmd_foo(int argc, const char **argv, const char *prefix);</tt></pre>
 570 </div></div>
 571 </li>
 572 <li>
 573 <p>
 574 Add the external declaration for the function to <tt>builtin.h</tt>.
 575 </p>
 576 </li>
 577 <li>
 578 <p>
 579 Add the command to <tt>commands[]</tt> table in <tt>handle_internal_command()</tt>,
 580   defined in <tt>git.c</tt>.  The entry should look like:
 581 </p>
 582 <div class="literalblock">
 583 <div class="content">
 584 <pre><tt>{ "foo", cmd_foo, &lt;options&gt; },</tt></pre>
 585 </div></div>
 586 <div class="paragraph"><p>where options is the bitwise-or of:</p></div>
 587 <div class="dlist"><dl>
 588 <dt class="hdlist1">
 589 <tt>RUN_SETUP</tt>
 590 </dt>
 591 <dd>
 592 <p>
 593         Make sure there is a git directory to work on, and if there is a
 594         work tree, chdir to the top of it if the command was invoked
 595         in a subdirectory.  If there is no work tree, no chdir() is
 596         done.
 597 </p>
 598 </dd>
 599 <dt class="hdlist1">
 600 <tt>USE_PAGER</tt>
 601 </dt>
 602 <dd>
 603 <p>
 604         If the standard output is connected to a tty, spawn a pager and
 605         feed our output to it.
 606 </p>
 607 </dd>
 608 <dt class="hdlist1">
 609 <tt>NEED_WORK_TREE</tt>
 610 </dt>
 611 <dd>
 612 <p>
 613         Make sure there is a work tree, i.e. the command cannot act
 614         on bare repositories.
 615         This only makes sense when <tt>RUN_SETUP</tt> is also set.
 616 </p>
 617 </dd>
 618 </dl></div>
 619 </li>
 620 <li>
 621 <p>
 622 Add <tt>builtin-foo.o</tt> to <tt>BUILTIN_OBJS</tt> in <tt>Makefile</tt>.
 623 </p>
 624 </li>
 625 </ol></div>
 626 <div class="paragraph"><p>Additionally, if <tt>foo</tt> is a new command, there are 3 more things to do:</p></div>
 627 <div class="olist arabic"><ol class="arabic">
 628 <li>
 629 <p>
 630 Add tests to <tt>t/</tt> directory.
 631 </p>
 632 </li>
 633 <li>
 634 <p>
 635 Write documentation in <tt>Documentation/git-foo.txt</tt>.
 636 </p>
 637 </li>
 638 <li>
 639 <p>
 640 Add an entry for <tt>git-foo</tt> to <tt>command-list.txt</tt>.
 641 </p>
 642 </li>
 643 <li>
 644 <p>
 645 Add an entry for <tt>/git-foo</tt> to <tt>.gitignore</tt>.
 646 </p>
 647 </li>
 648 </ol></div>
 649 </div>
 650 <h2 id="_how_a_built_in_is_called">How a built-in is called</h2>
 651 <div class="sectionbody">
 652 <div class="paragraph"><p>The implementation <tt>cmd_foo()</tt> takes three parameters, <tt>argc</tt>, <tt>argv,
 653 and `prefix</tt>.  The first two are similar to what <tt>main()</tt> of a
 654 standalone command would be called with.</p></div>
 655 <div class="paragraph"><p>When <tt>RUN_SETUP</tt> is specified in the <tt>commands[]</tt> table, and when you
 656 were started from a subdirectory of the work tree, <tt>cmd_foo()</tt> is called
 657 after chdir(2) to the top of the work tree, and <tt>prefix</tt> gets the path
 658 to the subdirectory the command started from.  This allows you to
 659 convert a user-supplied pathname (typically relative to that directory)
 660 to a pathname relative to the top of the work tree.</p></div>
 661 <div class="paragraph"><p>The return value from <tt>cmd_foo()</tt> becomes the exit status of the
 662 command.</p></div>
 663 </div>
 664 </div>
 665 <div id="footnotes"><hr /></div>
 666 <div id="footer">
 667 <div id="footer-text">
 668 Last updated 2011-09-21 23:01:14 PDT
 669 </div>
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