git-submodule summary: limit summary size
git-submodule summary: limit summary size

This patch teaches git-submodule an option '--summary-limit|-n <number>'
to limit number of commits in total for the summary of each submodule in
the modified case (only a single commit is shown in other cases).

Giving 0 will disable the summary; a negative number means unlimted, which
is the default.

Signed-off-by: Ping Yin <042bd97809d88aa56810834a9e2526d4839ab650@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git