file’s metadata We presume we can get modified time of diff files under any circumstances. list_saved_files doesn’t work if this presumption is not true.
We always have an archive of json src files which corresponds to save files. if there’s no change in json src files, we don’t need current src. if the src is changed, we need the archived and the current src because we need to update the save data and make it compatible with the current version. The current src can be specified as an archive or a directory.