Build the commit_list of parents by calling commit_list_append() twice
instead of allocating and linking the items by hand. This makes the
code shorter and simpler. Rename the commit_list from parent to parents
(plural) while at it because there are two of them.
Signed-off-by: Rene Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>