Add option to git-commit to allow empty log messages
Change git-commit(1) to accept the --allow-empty-message option
to allow a commit with an empty message. This is analogous to the
existing --allow-empty option which allows a commit that records
no changes. As these are mainly for interoperating with foreign SCM
systems, and are not meant for normal use, ensure that "git commit -h"
does not talk about them.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>