1builtin API 2=========== 3 4Adding a new built-in 5--------------------- 6 7There are 4 things to do to add a bulit-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 22 where 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. Add `builtin-foo.o` to `BUILTIN_OBJS` in `Makefile`. 37 38Additionally, if `foo` is a new command, there are 3 more things to do: 39 40. Add tests to `t/` directory. 41 42. Write documentation in `Documentation/git-foo.txt`. 43 44. Add an entry for `git-foo` to the list at the end of 45 `Documentation/cmd-list.perl`. 46 47 48How a built-in is called 49------------------------ 50 51The implementation `cmd_foo()` takes three parameters, `argc`, `argv, 52and `prefix`. The first two are similar to what `main()` of a 53standalone command would be called with. 54 55When `RUN_SETUP` is specified in the `commands[]` table, and when you 56were started from a subdirectory of the work tree, `cmd_foo()` is called 57after chdir(2) to the top of the work tree, and `prefix` gets the path 58to the subdirectory the command started from. This allows you to 59convert a user-supplied pathname (typically relative to that directory) 60to a pathname relative to the top of the work tree. 61 62The return value from `cmd_foo()` becomes the exit status of the 63command.