The straightforward way with using 'cat .git/refs/heads/*' doesn't work
with packed refs as well as branches of the form topic/topic1. So let's
use git-for-each-ref for getting the heads' SHA1s in this example.
Signed-off-by: Markus Heidelberg <markus.heidelberg@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>