code: def diff_handler(args):
      
  
      repo = _open_repo(args)
      anchor_id, anchor = _get_anchor(repo, args['<anchor-id>'])
  
      diff_lines = get_anchor_diff(anchor)
      sys.stdout.writelines(diff_lines)
  
      return ExitCode.OK
docs: usage: {program} diff <anchor-id>
  
      Show the difference between an anchor and the current state of the source.