Merge branch 'js/builtin-add-i'

The beginning of rewriting "git add -i" in C. * js/builtin-add-i: built-in add -i: implement the `help` command built-in add -i: use color in the main loop built-in add -i: support `?` (prompt help) built-in add -i: show unique prefixes of the commands built-in add -i: implement the main loop built-in add -i: color the header in the `status` command built-in add -i: implement the `status` command diff: export diffstat interface Start to implement a built-in version of `git add --interactive`