commit: avoid allocation in clear_commit_marks_many()

commit: avoid allocation in clear_commit_marks_many()

Pass the entries of the commit array directly to clear_commit_marks_1()
instead of adding them to a commit_list first.  The function clears the
commit and any first parent without allocation; only higher numbered
parents are added to a list for later treatment.  This change extends
that optimization to clear_commit_marks_many().

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>