git/technical/api-builtin.html at html · wolfpython/git · GitHub

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<title>builtin API</title>
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<body>
<div id="header">
<h1>builtin API</h1>
</div>
<h2 id="_adding_a_new_built_in">Adding a new built-in</h2>
<div class="sectionbody">
<div class="para"><p>There are 4 things to do to add a built-in command implementation to
git:</p></div>
<div class="olist"><ol>
<li>
<p>
Define the implementation of the built-in command <tt>foo</tt> with
  signature:
</p>
<div class="literalblock">
<div class="content">
<pre><tt>int cmd_foo(int argc, const char **argv, const char *prefix);</tt></pre>
</div></div>
</li>
<li>
<p>
Add the external declaration for the function to <tt>builtin.h</tt>.
</p>
</li>
<li>
<p>
Add the command to <tt>commands[]</tt> table in <tt>handle_internal_command()</tt>,
  defined in <tt>git.c</tt>.  The entry should look like:
</p>
<div class="literalblock">
<div class="content">
<pre><tt>{ "foo", cmd_foo, &lt;options&gt; },</tt></pre>
</div></div>
<div class="para"><p>where options is the bitwise-or of:</p></div>
<div class="vlist"><dl>
<dt>
<tt>RUN_SETUP</tt>
</dt>
<dd>
<p>
        Make sure there is a git directory to work on, and if there is a
        work tree, chdir to the top of it if the command was invoked
        in a subdirectory.  If there is no work tree, no chdir() is
        done.
</p>
</dd>
<dt>
<tt>USE_PAGER</tt>
</dt>
<dd>
<p>
        If the standard output is connected to a tty, spawn a pager and
        feed our output to it.
</p>
</dd>
<dt>
<tt>NEED_WORK_TREE</tt>
</dt>
<dd>
<p>
        Make sure there is a work tree, i.e. the command cannot act
        on bare repositories.
        This only makes sense when <tt>RUN_SETUP</tt> is also set.
</p>
</dd>
</dl></div>
</li>
<li>
<p>
Add <tt>builtin-foo.o</tt> to <tt>BUILTIN_OBJS</tt> in <tt>Makefile</tt>.
</p>
</li>
</ol></div>
<div class="para"><p>Additionally, if <tt>foo</tt> is a new command, there are 3 more things to do:</p></div>
<div class="olist"><ol>
<li>
<p>
Add tests to <tt>t/</tt> directory.
</p>
</li>
<li>
<p>
Write documentation in <tt>Documentation/git-foo.txt</tt>.
</p>
</li>
<li>
<p>
Add an entry for <tt>git-foo</tt> to <tt>command-list.txt</tt>.
</p>
</li>
</ol></div>
</div>
<h2 id="_how_a_built_in_is_called">How a built-in is called</h2>
<div class="sectionbody">
<div class="para"><p>The implementation <tt>cmd_foo()</tt> takes three parameters, <tt>argc</tt>, <tt>argv,
and `prefix</tt>.  The first two are similar to what <tt>main()</tt> of a
standalone command would be called with.</p></div>
<div class="para"><p>When <tt>RUN_SETUP</tt> is specified in the <tt>commands[]</tt> table, and when you
were started from a subdirectory of the work tree, <tt>cmd_foo()</tt> is called
after chdir(2) to the top of the work tree, and <tt>prefix</tt> gets the path
to the subdirectory the command started from.  This allows you to
convert a user-supplied pathname (typically relative to that directory)
to a pathname relative to the top of the work tree.</p></div>
<div class="para"><p>The return value from <tt>cmd_foo()</tt> becomes the exit status of the
command.</p></div>
</div>
<div id="footer">
<div id="footer-text">
Last updated 2010-09-18 23:57:09 UTC
</div>
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