If --no-checkout is specified, then the bisection process uses:
git update-ref --no-deref HEAD <trial>
at each trial instead of:
git checkout <trial>
Improved-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Jon Seymour <jon.seymour@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>