Just let the user know that a revision argument is missing instead of
a perl error. This error message mimic the "init" error message, but
could be improved.
Signed-off-by: Marc-Andre Lureau <marcandre.lureau@gmail.com> Acked-by: Eric Wong <normalperson@yhbt.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>