Merge branch 'py/submodule'

* py/submodule:
git-submodule summary: fix that some "wc" flavors produce leading spaces
git-submodule summary: test
git-submodule summary: documentation
git-submodule summary: limit summary size
git-submodule summary: show commit summary
git-submodule summary: code framework

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

diff --cc git-submodule.sh
Simple merge