Add version option handling

command.go

@@ -9,6 +9,7 @@ import (
 
 type Command struct {
 	Name             string
+	version          string
 	ShortDescription string
 	LongDescription  string
 	Aliases          []string
@@ -20,8 +21,8 @@ type Command struct {
 	isRoot           bool
 }
 
-func NewRoot(name string, options ...Option) *Command {
+func NewRoot(name string, version string, options ...Option) *Command {
-	cmd := &Command{Name: name, isRoot: true}
+	cmd := &Command{Name: name, version: version, isRoot: true}
 	cmd.ApplyOptions(options...)
 	return cmd
 }
@@ -91,6 +92,12 @@ func (c *Command) Execute(args []string) {
 		os.Exit(1)
 	}
 
+	versionOpt, ok := opt.Globals().GetBool("version")
+	if ok && versionOpt.Value() {
+		c.ShowVersion()
+		return
+	}
+
 	helpOpt, ok := opt.Globals().GetBool("help")
 	if ok && helpOpt.Value() {
 		c.ShowHelp()
@@ -104,3 +111,8 @@ func (c *Command) Execute(args []string) {
 
 	c.ShowHelp()
 }
+
+func (c *Command) ShowVersion() {
+	rootName := c.Root().Name
+	fmt.Printf("%s %s\n", rootName, c.version)
+}