Allow the api-version on the command to override the client builder

pkg/client/clientcmd/client_builder_test.go

@@ -29,6 +29,7 @@ import (
 	"github.com/spf13/pflag"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/latest"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/clientauth"
 )
 
@@ -251,6 +252,40 @@ func TestLoadClientAuthInfoOrPrompt(t *testing.T) {
 	}
 }
 
+func TestOverride(t *testing.T) {
+	b := NewBuilder(nil)
+	cfg, err := b.Config()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if cfg.Version != "" {
+		t.Errorf("unexpected default config version")
+	}
+
+	newCfg, err := b.Override(func(cfg *client.Config) {
+		if cfg.Version != "" {
+			t.Errorf("unexpected default config version")
+		}
+		cfg.Version = "test"
+	}).Config()
+
+	if newCfg.Version != "test" {
+		t.Errorf("unexpected override config version")
+	}
+
+	if cfg.Version != "" {
+		t.Errorf("original object should not change")
+	}
+
+	cfg, err = b.Config()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if cfg.Version != "" {
+		t.Errorf("override should not be persistent")
+	}
+}
+
 func matchStringArg(expected, got string, t *testing.T) {
 	if expected != got {
 		t.Errorf("Expected %v, got %v", expected, got)