docs: def track(context, file_names):
      """Keep track of each file in list file_names.
  
      Tracking does not create or delete the actual file, it only tells the
      version control system whether to maintain versions (to keep track) of
      the file.
      """
      context.obj.find_repo_type()
      for fn in file_names:
          context.obj.call([context.obj.vc_name, 'add', fn])