enhanced default cluster selection, add 'cluster switch', overhaul json header setting (#47)

cmd/root.go

@@ -122,7 +122,10 @@ func Main() int {
 
 		Before: func(ctx context.Context, cmd *cli.Command) (context.Context, error) {
 			if tree {
-				Tree(cmd)
+				if err := Tree(cmd); err != nil {
+					return nil, err
+				}
+
 				os.Exit(0)
 			}
 
@@ -254,7 +257,7 @@ func Debug(conf *cfg.Config) *cli.Command {
 func Tree(cmd *cli.Command) error {
 	max := 20
 
-	cmd.Walk(func(cmd *cli.Command) error {
+	return cmd.Walk(func(cmd *cli.Command) error {
 		path := cmd.Path()
 		command := path[len(path)-1]
 
@@ -269,6 +272,4 @@ func Tree(cmd *cli.Command) error {
 
 		return nil
 	})
-
-	return nil
 }