Merge branch 'ma/leakplugs'

Memory leaks in various codepaths have been plugged.

* ma/leakplugs:
  pack-bitmap[-write]: use `object_array_clear()`, don't leak
  object_array: add and use `object_array_pop()`
  object_array: use `object_array_clear()`, not `free()`
  leak_pending: use `object_array_clear()`, not `free()`
  commit: fix memory leak in `reduce_heads()`
  builtin/commit: fix memory leak in `prepare_index()`

bisect.c

@@ -826,7 +826,8 @@ static int check_ancestors(const char *prefix)
 
 	/* Clean up objects used, as they will be reused. */
 	clear_commit_marks_for_object_array(&pending_copy, ALL_REV_FLAGS);
-	free(pending_copy.objects);
+
+	object_array_clear(&pending_copy);
 
 	return res;
 }