code: func (c *commonFlags) Init(authOpts auth.Options) {
  	c.defaultFlags.Init(&c.Flags)
  	c.authFlags.Register(&c.Flags, authOpts)
  	c.Flags.StringVar(&c.serverURL, "server", os.Getenv("SWARMING_SERVER"), "Server URL; required. Set $SWARMING_SERVER to set a default.")
  	c.Flags.IntVar(&c.worker, "worker", 8, "Number of workers used to download isolated files.")
  }
docs: // Init initializes common flags.