This patch simplifies Brian's fix for the recent regression by:

* eliminating the extra loop
* eliminating use of git rev-parse for parsing flags
* making use of the for opt idiom for the retained loop
* eliminating the redundant -- case

The patch has been tested with the tests in current maint.
Signed-off-by: NJon Seymour <jon.seymour@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>