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735 <body class="article">
736 <div id="header">
737 <h1>How to integrate new subcommands</h1>
738 <span id="revdate">2024-06-12</span>
739 </div>
740 <div id="content">
741 <div id="preamble">
742 <div class="sectionbody">
743 <div class="paragraph"><p>This is how-to documentation for people who want to add extension
744 commands to Git. It should be read alongside builtin.h.</p></div>
745 </div>
746 </div>
747 <div class="sect1">
748 <h2 id="_runtime_environment">Runtime environment</h2>
749 <div class="sectionbody">
750 <div class="paragraph"><p>Git subcommands are standalone executables that live in the Git exec
751 path, normally /usr/lib/git-core. The git executable itself is a
752 thin wrapper that knows where the subcommands live, and runs them by
753 passing command-line arguments to them.</p></div>
754 <div class="paragraph"><p>(If "git foo" is not found in the Git exec path, the wrapper
755 will look in the rest of your $PATH for it. Thus, it&#8217;s possible
756 to write local Git extensions that don&#8217;t live in system space.)</p></div>
757 </div>
758 </div>
759 <div class="sect1">
760 <h2 id="_implementation_languages">Implementation languages</h2>
761 <div class="sectionbody">
762 <div class="paragraph"><p>Most subcommands are written in C or shell. A few are written in
763 Perl.</p></div>
764 <div class="paragraph"><p>While we strongly encourage coding in portable C for portability,
765 these specific scripting languages are also acceptable. We won&#8217;t
766 accept more without a very strong technical case, as we don&#8217;t want
767 to broaden the Git suite&#8217;s required dependencies. Import utilities,
768 surgical tools, remote helpers and other code at the edges of the
769 Git suite are more lenient and we allow Python (and even Tcl/tk),
770 but they should not be used for core functions.</p></div>
771 <div class="paragraph"><p>This may change in the future. Especially Python is not allowed in
772 core because we need better Python integration in the Git Windows
773 installer before we can be confident people in that environment
774 won&#8217;t experience an unacceptably large loss of capability.</p></div>
775 <div class="paragraph"><p>C commands are normally written as single modules, named after the
776 command, that link a collection of functions called libgit. Thus,
777 your command <em>git-foo</em> would normally be implemented as a single
778 "git-foo.c" (or "builtin/foo.c" if it is to be linked to the main
779 binary); this organization makes it easy for people reading the code
780 to find things.</p></div>
781 <div class="paragraph"><p>See the CodingGuidelines document for other guidance on what we consider
782 good practice in C and shell, and api-builtin.txt for the support
783 functions available to built-in commands written in C.</p></div>
784 </div>
785 </div>
786 <div class="sect1">
787 <h2 id="_what_every_extension_command_needs">What every extension command needs</h2>
788 <div class="sectionbody">
789 <div class="paragraph"><p>You must have a man page, written in asciidoc (this is what Git help
790 followed by your subcommand name will display). Be aware that there is
791 a local asciidoc configuration and macros which you should use. It&#8217;s
792 often helpful to start by cloning an existing page and replacing the
793 text content.</p></div>
794 <div class="paragraph"><p>You must have a test, written to report in TAP (Test Anything Protocol).
795 Tests are executables (usually shell scripts) that live in the <em>t</em>
796 subdirectory of the tree. Each test name begins with <em>t</em> and a sequence
797 number that controls where in the test sequence it will be executed;
798 conventionally the rest of the name stem is that of the command
799 being tested.</p></div>
800 <div class="paragraph"><p>Read the file t/README to learn more about the conventions to be used
801 in writing tests, and the test support library.</p></div>
802 </div>
803 </div>
804 <div class="sect1">
805 <h2 id="_integrating_a_command">Integrating a command</h2>
806 <div class="sectionbody">
807 <div class="paragraph"><p>Here are the things you need to do when you want to merge a new
808 subcommand into the Git tree.</p></div>
809 <div class="olist arabic"><ol class="arabic">
810 <li>
812 Don&#8217;t forget to sign off your patch!
813 </p>
814 </li>
815 <li>
817 Append your command name to one of the variables BUILTIN_OBJS,
818 EXTRA_PROGRAMS, SCRIPT_SH, SCRIPT_PERL or SCRIPT_PYTHON.
819 </p>
820 </li>
821 <li>
823 Drop its test in the t directory.
824 </p>
825 </li>
826 <li>
828 If your command is implemented in an interpreted language with a
829 p-code intermediate form, make sure .gitignore in the main directory
830 includes a pattern entry that ignores such files. Python .pyc and
831 .pyo files will already be covered.
832 </p>
833 </li>
834 <li>
836 If your command has any dependency on a particular version of
837 your language, document it in the INSTALL file.
838 </p>
839 </li>
840 <li>
842 There is a file command-list.txt in the distribution main directory
843 that categorizes commands by type, so they can be listed in appropriate
844 subsections in the documentation&#8217;s summary command list. Add an entry
845 for yours. To understand the categories, look at command-list.txt
846 in the main directory. If the new command is part of the typical Git
847 workflow and you believe it common enough to be mentioned in <em>git help</em>,
848 map this command to a common group in the column [common].
849 </p>
850 </li>
851 <li>
853 Give the maintainer one paragraph to include in the RelNotes file
854 to describe the new feature; a good place to do so is in the cover
855 letter [PATCH 0/n].
856 </p>
857 </li>
858 </ol></div>
859 <div class="paragraph"><p>That&#8217;s all there is to it.</p></div>
860 </div>
861 </div>
862 </div>
863 <div id="footnotes"><hr /></div>
864 <div id="footer">
865 <div id="footer-text">
866 Last updated
867 2024-06-12 15:16:12 PDT
868 </div>
869 </div>
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