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 the `commands[]` table defined in `git.c`. 18 The entry should look like: 19 20 { "foo", cmd_foo, <options> }, 21+ 22where options is the bitwise-or of: 23 24`RUN_SETUP`:: 25 If there is not a Git directory to work on, abort. If there 26 is a work tree, chdir to the top of it if the command was 27 invoked in a subdirectory. If there is no work tree, no 28 chdir() is done. 29 30`RUN_SETUP_GENTLY`:: 31 If there is a Git directory, chdir as per RUN_SETUP, otherwise, 32 don't chdir anywhere. 33 34`USE_PAGER`:: 35 36 If the standard output is connected to a tty, spawn a pager and 37 feed our output to it. 38 39`NEED_WORK_TREE`:: 40 41 Make sure there is a work tree, i.e. the command cannot act 42 on bare repositories. 43 This only makes sense when `RUN_SETUP` is also set. 44 45. Add `builtin/foo.o` to `BUILTIN_OBJS` in `Makefile`. 46 47Additionally, if `foo` is a new command, there are 3 more things to do: 48 49. Add tests to `t/` directory. 50 51. Write documentation in `Documentation/git-foo.txt`. 52 53. Add an entry for `git-foo` to `command-list.txt`. 54 55. Add an entry for `/git-foo` to `.gitignore`. 56 57 58How a built-in is called 59------------------------ 60 61The implementation `cmd_foo()` takes three parameters, `argc`, `argv, 62and `prefix`. The first two are similar to what `main()` of a 63standalone command would be called with. 64 65When `RUN_SETUP` is specified in the `commands[]` table, and when you 66were started from a subdirectory of the work tree, `cmd_foo()` is called 67after chdir(2) to the top of the work tree, and `prefix` gets the path 68to the subdirectory the command started from. This allows you to 69convert a user-supplied pathname (typically relative to that directory) 70to a pathname relative to the top of the work tree. 71 72The return value from `cmd_foo()` becomes the exit status of the 73command.