code: func (c *commonFlags) Parse() error {
  	if err := c.defaultFlags.Parse(); err != nil {
  		return err
  	}
  	if c.serverURL == "" {
  		return errors.Reason("must provide -server").Err()
  	}
  	s, err := lhttp.CheckURL(c.serverURL)
  	if err != nil {
  		return err
  	}
  	c.serverURL = s
  	c.parsedAuthOpts, err = c.authFlags.Options()
  	return err
  }
docs: // Parse parses the common flags.