code: func cmdInstalled(params Parameters) *subcommands.Command {
  	return &subcommands.Command{
  		Advanced:  true,
  		UsageLine: "installed [options]",
  		ShortDesc: "lists packages installed in the site root",
  		LongDesc:  "Lists packages installed in the site root.",
  		CommandRun: func() subcommands.CommandRun {
  			c := &installedRun{defaultServiceURL: params.ServiceURL}
  			c.registerBaseFlags()
  			c.siteRootOptions.registerFlags(&c.Flags)
  			return c
  		},
  	}
  }
docs: ////////////////////////////////////////////////////////////////////////////////
  // 'installed' subcommand.