diff-tree: convert diff_tree_sha1 to struct object_id

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/revision.c b/revision.c
index 7637e75..3030f33 100644
--- a/revision.c
+++ b/revision.c
@@ -455,7 +455,7 @@ static int rev_compare_tree(struct rev_info *revs,
 
 	tree_difference = REV_TREE_SAME;
 	DIFF_OPT_CLR(&revs->pruning, HAS_CHANGES);
-	if (diff_tree_sha1(t1->object.oid.hash, t2->object.oid.hash, "",
+	if (diff_tree_oid(&t1->object.oid, &t2->object.oid, "",
 			   &revs->pruning) < 0)
 		return REV_TREE_DIFFERENT;
 	return tree_difference;
@@ -471,7 +471,7 @@ static int rev_same_tree_as_empty(struct rev_info *revs, struct commit *commit)
 
 	tree_difference = REV_TREE_SAME;
 	DIFF_OPT_CLR(&revs->pruning, HAS_CHANGES);
-	retval = diff_tree_sha1(NULL, t1->object.oid.hash, "", &revs->pruning);
+	retval = diff_tree_oid(NULL, &t1->object.oid, "", &revs->pruning);
 
 	return retval >= 0 && (tree_difference == REV_TREE_SAME);
 }