code: func (s *Action) ConfigComplete(c *cli.Context) {
  	cm := s.cfg.Root.ConfigMap()
  	keys := make([]string, 0, len(cm))
  	for k := range cm {
  		keys = append(keys, k)
  	}
  	sort.Strings(keys)
  	for _, k := range keys {
  		fmt.Fprintln(stdout, k)
  	}
  }
docs: // ConfigComplete will print the list of valid config keys