Refactor the client (again) to better support auth

* Allows consumers to provide their own transports for common cases.
* Supports KUBE_API_VERSION on test cases for controlling which
  api version they test against
* Provides a common flag registration method for CLIs that need
  to connect to an API server (to avoid duplicating flags)
* Ensures errors are properly returned by the server
* Add a Context field to client.Config

pkg/api/testapi/testapi.go

@@ -0,0 +1,42 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package testapi provides a helper for retrieving the KUBE_API_VERSION environment variable.
+package testapi
+
+import (
+	"os"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/latest"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
+)
+
+// Version returns the API version to test against as set by the KUBE_API_VERSION env var.
+func Version() string {
+	version := os.Getenv("KUBE_API_VERSION")
+	if version == "" {
+		version = latest.Version
+	}
+	return version
+}
+
+func CodecForVersionOrDie() runtime.Codec {
+	interfaces, err := latest.InterfacesFor(Version())
+	if err != nil {
+		panic(err)
+	}
+	return interfaces.Codec
+}