Add utility function to get port forwarded tiller hostname

I didn't change any binaries to use this to minimize possible conflicts.
Main purpose of adding this is to simplify external developers creating
a helm client.

pkg/helm/client.go

@@ -17,6 +17,7 @@ limitations under the License.
 package helm // import "k8s.io/helm/pkg/helm"
 
 import (
+	"fmt"
 	"io"
 	"time"
 
@@ -25,9 +26,14 @@ import (
 	"google.golang.org/grpc/credentials"
 	"google.golang.org/grpc/keepalive"
 
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
 	"k8s.io/helm/pkg/chartutil"
+	"k8s.io/helm/pkg/helm/portforwarder"
+	"k8s.io/helm/pkg/kube"
 	"k8s.io/helm/pkg/proto/hapi/chart"
 	rls "k8s.io/helm/pkg/proto/hapi/services"
+	"k8s.io/helm/pkg/tiller/environment"
 )
 
 // maxMsgSize use 20MB as the default message size limit.
@@ -39,6 +45,32 @@ type Client struct {
 	opts options
 }
 
+// TillerHost returns a port forwarded tiller hostname
+func TillerHost(namespace, context string) (string, error) {
+	config, err := rest.InClusterConfig()
+	if err != nil {
+		config, err = kube.GetConfig(context).ClientConfig()
+	}
+	if err != nil {
+		return "", fmt.Errorf("could not get Kubernetes config for context %q: %s", context, err)
+	}
+
+	client, err := kubernetes.NewForConfig(config)
+	if err != nil {
+		return "", fmt.Errorf("could not get Kubernetes client: %s", err)
+	}
+
+	if namespace == "" {
+		namespace = environment.DefaultTillerNamespace
+	}
+	tunnel, err := portforwarder.New(namespace, client, config)
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("127.0.0.1:%d", tunnel.Local), nil
+}
+
 // NewClient creates a new client.
 func NewClient(opts ...Option) *Client {
 	var c Client