Only the first 'remote' head is currently specified as an argument to 'git
log' when generating a SQUSH_MSG, which makes the generated message fail
to mention every commit involved in the merge. This fixes the problem.
Noticed-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Lars Hjemli <hjemli@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>