docs: def jpegrescan(ext_args):
      """Run the EXTERNAL program jpegrescan."""
      args = copy.copy(_JPEGRESCAN_ARGS)
      if Settings.jpegrescan_multithread:
          args += ['-t']
      if Settings.destroy_metadata:
          args += ['-s']
      args += [ext_args.old_filename, ext_args.new_filename]
      extern.run_ext(args)
      return _JPEG_FORMAT