pretty_print_commit: honor grafts.
pretty_print_commit: honor grafts.

When displaying Merge: lines, we used to take the real commit
parents from the commit objects.  Use the parsed parents from
the commit object instead, so that we honor fake parent
information from info/grafts.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git