This also removes the superfluous "specify" and rewords the misleading
"if any" which sounds as if omitting "-m" would omit the merge commit
message. (It means "if a merge commit is created at all".)
Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>