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 <pkufranky@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>