code: func Cmd(params base.Parameters) *subcommands.Command {
  	return &subcommands.Command{
  		UsageLine: "validate [CONFIG_DIR|SCRIPT]",
  		ShortDesc: "sends configuration files to LUCI Config service for validation",
  		LongDesc: `Sends configuration files to LUCI Config service for validation.
  
  If the first positional argument is a directory, takes all files there and
  sends them to LUCI Config service, to be validated as a single config set. The
  name of the config set (e.g. "projects/foo") MUST be provided via -config-set
  flag, it is required in this mode.
  
  If the first positional argument is a Starlark file, it is interpreted (as with
  'generate' subcommand) and the resulting generated configs are compared to
  what's already on disk in -config-dir directory. If they are different, the
  subcommand exits with non-zero exit code (indicating files on disk are stale).
  Otherwise the configs are sent to LUCI Config service for validation.
  Partitioning into config sets is specified in the Starlark code in this case,
  -config-set flag is rejected if given.
  
  When interpreting Starlark script, flags like -config-dir and -fail-on-warnings
  work as overrides for values declared in the script via lucicfg.config(...)
  statement. See its doc for more details.
  		`,
  		CommandRun: func() subcommands.CommandRun {
  			vr := &validateRun{}
  			vr.Init(params)
  			vr.AddMetaFlags()
  			vr.Flags.StringVar(&vr.configSet, "config-set", "",
  				"Name of the config set to validate against when validating existing *.cfg configs.")
  			return vr
  		},
  	}
  }
docs: // Cmd is 'validate' subcommand.