106 lines
4.4 KiB
Text
106 lines
4.4 KiB
Text
From: Eric S. Raymond <esr@thyrsus.com>
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Abstract: This is how-to documentation for people who want to add extension
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commands to Git. It should be read alongside api-builtin.txt.
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Content-type: text/asciidoc
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How to integrate new subcommands
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================================
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This is how-to documentation for people who want to add extension
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commands to Git. It should be read alongside api-builtin.txt.
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Runtime environment
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-------------------
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Git subcommands are standalone executables that live in the Git exec
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path, normally /usr/lib/git-core. The git executable itself is a
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thin wrapper that knows where the subcommands live, and runs them by
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passing command-line arguments to them.
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(If "git foo" is not found in the Git exec path, the wrapper
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will look in the rest of your $PATH for it. Thus, it's possible
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to write local Git extensions that don't live in system space.)
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Implementation languages
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------------------------
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Most subcommands are written in C or shell. A few are written in
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Perl.
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While we strongly encourage coding in portable C for portability,
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these specific scripting languages are also acceptable. We won't
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accept more without a very strong technical case, as we don't want
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to broaden the Git suite's required dependencies. Import utilities,
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surgical tools, remote helpers and other code at the edges of the
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Git suite are more lenient and we allow Python (and even Tcl/tk),
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but they should not be used for core functions.
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This may change in the future. Especially Python is not allowed in
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core because we need better Python integration in the Git Windows
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installer before we can be confident people in that environment
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won't experience an unacceptably large loss of capability.
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C commands are normally written as single modules, named after the
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command, that link a collection of functions called libgit. Thus,
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your command 'git-foo' would normally be implemented as a single
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"git-foo.c" (or "builtin/foo.c" if it is to be linked to the main
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binary); this organization makes it easy for people reading the code
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to find things.
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See the CodingGuidelines document for other guidance on what we consider
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good practice in C and shell, and api-builtin.txt for the support
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functions available to built-in commands written in C.
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What every extension command needs
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----------------------------------
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You must have a man page, written in asciidoc (this is what Git help
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followed by your subcommand name will display). Be aware that there is
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a local asciidoc configuration and macros which you should use. It's
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often helpful to start by cloning an existing page and replacing the
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text content.
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You must have a test, written to report in TAP (Test Anything Protocol).
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Tests are executables (usually shell scripts) that live in the 't'
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subdirectory of the tree. Each test name begins with 't' and a sequence
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number that controls where in the test sequence it will be executed;
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conventionally the rest of the name stem is that of the command
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being tested.
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Read the file t/README to learn more about the conventions to be used
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in writing tests, and the test support library.
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Integrating a command
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---------------------
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Here are the things you need to do when you want to merge a new
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subcommand into the Git tree.
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1. Don't forget to sign off your patch!
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2. Append your command name to one of the variables BUILTIN_OBJS,
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EXTRA_PROGRAMS, SCRIPT_SH, SCRIPT_PERL or SCRIPT_PYTHON.
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3. Drop its test in the t directory.
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4. If your command is implemented in an interpreted language with a
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p-code intermediate form, make sure .gitignore in the main directory
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includes a pattern entry that ignores such files. Python .pyc and
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.pyo files will already be covered.
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5. If your command has any dependency on a particular version of
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your language, document it in the INSTALL file.
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6. There is a file command-list.txt in the distribution main directory
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that categorizes commands by type, so they can be listed in appropriate
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subsections in the documentation's summary command list. Add an entry
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for yours. To understand the categories, look at command-list.txt
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in the main directory. If the new command is part of the typical Git
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workflow and you believe it common enough to be mentioned in 'git help',
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map this command to a common group in the column [common].
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7. Give the maintainer one paragraph to include in the RelNotes file
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to describe the new feature; a good place to do so is in the cover
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letter [PATCH 0/n].
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That's all there is to it.
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