+static int compare_tree(struct tree *t1, struct tree *t2)
+{
+ if (!t1)
+ return TREE_NEW;
+ if (!t2)
+ return TREE_DIFFERENT;
+ tree_difference = TREE_SAME;
+ if (diff_tree_sha1(t1->object.sha1, t2->object.sha1, "", &diff_opt) < 0)
+ return TREE_DIFFERENT;
+ return tree_difference;
+}
+
+static int same_tree_as_empty(struct tree *t1)
+{
+ int retval;
+ void *tree;
+ struct tree_desc empty, real;
+
+ if (!t1)
+ return 0;
+
+ tree = read_object_with_reference(t1->object.sha1, "tree", &real.size, NULL);
+ if (!tree)
+ return 0;
+ real.buf = tree;
+
+ empty.buf = "";
+ empty.size = 0;
+
+ tree_difference = 0;
+ retval = diff_tree(&empty, &real, "", &diff_opt);
+ free(tree);
+
+ return retval >= 0 && !tree_difference;
+}
+
+static void try_to_simplify_commit(struct commit *commit)