1builtin API 2=========== 3 4Adding a new built-in 5--------------------- 6 7There are 4 things to do to add a built-in command implementation to 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> }, 21+ 22where options is the bitwise-or of: 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 36`NEED_WORK_TREE`:: 37 38 Make sure there is a work tree, i.e. the command cannot act 39 on bare repositories. 40 This only makes sense when `RUN_SETUP` is also set. 41 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 50. Add an entry for `git-foo` to `command-list.txt`. 51 52. Add an entry for `/git-foo` to `.gitignore`. 53 54 55How a built-in is called 56------------------------ 57 58The implementation `cmd_foo()` takes three parameters, `argc`, `argv, 59and `prefix`. The first two are similar to what `main()` of a 60standalone command would be called with. 61 62When `RUN_SETUP` is specified in the `commands[]` table, and when you 63were started from a subdirectory of the work tree, `cmd_foo()` is called 64after chdir(2) to the top of the work tree, and `prefix` gets the path 65to the subdirectory the command started from. This allows you to 66convert a user-supplied pathname (typically relative to that directory) 67to a pathname relative to the top of the work tree. 68 69The return value from `cmd_foo()` becomes the exit status of the 70command.