code: def untrack(context, file_names):
      
      context.obj.find_repo_type()
      for fn in file_names:
          if context.obj.vc_name == 'git':
              context.obj.call(['git', 'rm', '--cached', fn])
          elif context.obj.vc_name == 'hg':
              context.obj.call(['hg', 'forget', fn])
docs: Forget about tracking each file in the 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.