code: func cmdInstances(params Parameters) *subcommands.Command {
  	return &subcommands.Command{
  		UsageLine: "instances <package> [-limit ...]",
  		ShortDesc: "lists instances of a package",
  		LongDesc:  "Lists instances of a package, most recently uploaded first.",
  		CommandRun: func() subcommands.CommandRun {
  			c := &instancesRun{}
  			c.registerBaseFlags()
  			c.clientOptions.registerFlags(&c.Flags, params, withoutRootDir)
  			c.Flags.IntVar(&c.limit, "limit", 20, "How many instances to return or 0 for all.")
  			return c
  		},
  	}
  }
docs: ////////////////////////////////////////////////////////////////////////////////
  // 'instances' subcommand.