Merge pull request #24 from feloy/version

Add --version option

Author: ahmetb

cmd/kubectl-tree/rootcmd.go

@@ -32,15 +32,29 @@ import (
 
 var cf *genericclioptions.ConfigFlags
 
+// This variable is populated by goreleaser
+var version string
+
 // rootCmd represents the base command when called without any subcommands
 var rootCmd = &cobra.Command{
 	Use:          "kubectl tree KIND NAME",
 	SilenceUsage: true, // for when RunE returns an error
 	Short:        "Show sub-resources of the Kubernetes object",
 	Example: "  kubectl tree deployment my-app\n" +
 		"  kubectl tree kservice.v1.serving.knative.dev my-app", // TODO add more examples about disambiguation etc
-	Args: cobra.MinimumNArgs(2),
-	RunE: run,
+	Args:    cobra.MinimumNArgs(2),
+	RunE:    run,
+	Version: versionString(),
+}
+
+// versionString returns the version prefixed by 'v'
+// or an empty string if no version has been populated by goreleaser.
+// In this case, the --version flag will not be added by cobra.
+func versionString() string {
+	if len(version) == 0 {
+		return ""
+	}
+	return "v" + version
 }
 
 func run(_ *cobra.Command, args []string) error {