It is convention that argv should be terminated with NULL, even if
argc is used to specify the size of argv. setup_revisions() requires
this and may segfault otherwise.
This patch makes sure that all argv (that I can find) is NULL terminated.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>