Use Cobra built-in --version feature

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/cobra.go

@@ -22,6 +22,7 @@ func SetupRootCommand(rootCmd *cobra.Command) {
 	rootCmd.SetHelpTemplate(helpTemplate)
 	rootCmd.SetFlagErrorFunc(FlagErrorFunc)
 	rootCmd.SetHelpCommand(helpCommand)
+	rootCmd.SetVersionTemplate("Docker version {{.Version}}\n")
 
 	rootCmd.PersistentFlags().BoolP("help", "h", false, "Print usage")
 	rootCmd.PersistentFlags().MarkShorthandDeprecated("help", "please use --help")

cmd/dockerd/docker.go

@@ -24,19 +24,16 @@ func newDaemonCommand() *cobra.Command {
 		SilenceErrors: true,
 		Args:          cli.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if opts.version {
-				showVersion()
-				return nil
-			}
 			opts.flags = cmd.Flags()
 			return runDaemon(opts)
 		},
 		DisableFlagsInUseLine: true,
+		Version:               fmt.Sprintf("%s, build %s", dockerversion.Version, dockerversion.GitCommit),
 	}
 	cli.SetupRootCommand(cmd)
 
 	flags := cmd.Flags()
-	flags.BoolVarP(&opts.version, "version", "v", false, "Print version information and quit")
+	flags.BoolP("version", "v", false, "Print version information and quit")
 	flags.StringVar(&opts.configFile, "config-file", defaultDaemonConfigFile, "Daemon configuration file")
 	opts.InstallFlags(flags)
 	installConfigFlags(opts.daemonConfig, flags)
@@ -45,10 +42,6 @@ func newDaemonCommand() *cobra.Command {
 	return cmd
 }
 
-func showVersion() {
-	fmt.Printf("Docker version %s, build %s\n", dockerversion.Version, dockerversion.GitCommit)
-}
-
 func main() {
 	if reexec.Init() {
 		return

cmd/dockerd/options.go

@@ -30,7 +30,6 @@ var (
 )
 
 type daemonOptions struct {
-	version      bool
 	configFile   string
 	daemonConfig *config.Config
 	flags        *pflag.FlagSet