revision.c: make --date-order overriddable

Jan Engelhardt noticed that while --topo-order can be overridden by a
subsequent --date-order, the reverse was not possible. That's because
setup_revisions() failed to set revs->lifo properly.

Signed-off-by: Michele Ballabio <barra_cuda@katamail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

revision.c

@@ -1019,6 +1019,7 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, const ch
 				continue;
 			}
 			if (!strcmp(arg, "--topo-order")) {
+				revs->lifo = 1;
 				revs->topo_order = 1;
 				continue;
 			}