These macros allow us to add extra parse-options flag, the main one in
my mind is PARSE_OPT_NOCOMPLETE to hide certain options from
--git-completion-helper.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>