Merge branch 'pc/submodule-helper'

GSoC.

* pc/submodule-helper:
submodule: port submodule subcommand 'status' from shell to C
submodule--helper: introduce for_each_listed_submodule()
submodule--helper: introduce get_submodule_displaypath()

diff --cc builtin/submodule--helper.c
Simple merge