Documentation: fix a grammatical error in api-builtin.txt
[git/git.git] / Documentation / technical / api-builtin.txt
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1builtin API
2===========
3
4Adding a new built-in
5---------------------
6
82936f29 7There are 4 things to do to add a built-in command implementation to
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8git:
9
10. Define the implementation of the built-in command `foo` with
11 signature:
12
13 int cmd_foo(int argc, const char **argv, const char *prefix);
14
15. Add the external declaration for the function to `builtin.h`.
16
17. Add the command to `commands[]` table in `handle_internal_command()`,
18 defined in `git.c`. The entry should look like:
19
20 { "foo", cmd_foo, <options> },
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21+
22where options is the bitwise-or of:
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23
24`RUN_SETUP`::
25
26 Make sure there is a git directory to work on, and if there is a
27 work tree, chdir to the top of it if the command was invoked
28 in a subdirectory. If there is no work tree, no chdir() is
29 done.
30
31`USE_PAGER`::
32
33 If the standard output is connected to a tty, spawn a pager and
34 feed our output to it.
35
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36`NEED_WORK_TREE`::
37
38 Make sure there is a work tree, i.e. the command cannot act
39 on bare repositories.
d649048e 40 This only makes sense when `RUN_SETUP` is also set.
82936f29 41
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42. Add `builtin-foo.o` to `BUILTIN_OBJS` in `Makefile`.
43
44Additionally, if `foo` is a new command, there are 3 more things to do:
45
46. Add tests to `t/` directory.
47
48. Write documentation in `Documentation/git-foo.txt`.
49
82936f29 50. Add an entry for `git-foo` to `command-list.txt`.
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51
52
53How a built-in is called
54------------------------
55
56The implementation `cmd_foo()` takes three parameters, `argc`, `argv,
57and `prefix`. The first two are similar to what `main()` of a
58standalone command would be called with.
59
60When `RUN_SETUP` is specified in the `commands[]` table, and when you
61were started from a subdirectory of the work tree, `cmd_foo()` is called
62after chdir(2) to the top of the work tree, and `prefix` gets the path
63to the subdirectory the command started from. This allows you to
64convert a user-supplied pathname (typically relative to that directory)
65to a pathname relative to the top of the work tree.
66
67The return value from `cmd_foo()` becomes the exit status of the
68command.