Merge branch 'pc/submodule-helper-foreach'

The bulk of "git submodule foreach" has been rewritten in C.

* pc/submodule-helper-foreach:
  submodule: port submodule subcommand 'foreach' from shell to C
  submodule foreach: document variable '$displaypath'
  submodule foreach: document '$sm_path' instead of '$path'
  submodule foreach: correct '$path' in nested submodules from a subdirectory

diff --cc Documentation/git-submodule.txt
Simple merge

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

diff --cc git-submodule.sh
Simple merge