allow kubectl to be built statically

* Package kubectl in a container
* Add example with a pod using kubectl as a sidecar

kubectl-container/.gitignore

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+kubectl
+.tag

kubectl-container/Dockerfile

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+# 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.
+
+FROM scratch
+MAINTAINER Daniel Smith <dbsmith@google.com>
+ADD kubectl kubectl
+ENTRYPOINT ["/kubectl"]

kubectl-container/Makefile

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+# Use:
+#
+# `make kubectl` will build kubectl.
+# `make tag` will suggest a tag.
+# `make container` will build a container-- you must supply a tag.
+# `make push` will push the container-- you must supply a tag.
+
+kubectl:
+	KUBE_STATIC_OVERRIDES="kubectl" ../../hack/build-go.sh cmd/kubectl; cp ../../_output/local/bin/linux/amd64/kubectl .
+
+.tag: kubectl
+	./kubectl version -c | grep -o 'GitVersion:"[^"]*"' | cut -f 2 -d '"' > .tag
+
+tag: .tag
+	@echo "Suggest using TAG=$(shell cat .tag)"
+	@echo "$$ make container TAG=$(shell cat .tag)"
+	@echo "or"
+	@echo "$$ make push TAG=$(shell cat .tag)"
+
+container:
+	$(if $(TAG),,$(error TAG is not defined. Use 'make tag' to see a suggestion))
+	docker build -t gcr.io/google_containers/kubectl:$(TAG) .
+
+push: container
+	$(if $(TAG),,$(error TAG is not defined. Use 'make tag' to see a suggestion))
+	gcloud preview docker push gcr.io/google_containers/kubectl:$(TAG)
+
+clean:
+	rm -f kubectl
+	rm -f .tag

kubectl-container/README.md

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+This directory contains a Dockerfile and Makefile for packaging up kubectl into
+a container.
+
+It's not currently automated as part of a release process, so for the moment
+this is an example of what to do if you want to package kubectl into a
+container/your pod.
+
+In the future, we may release consistently versioned groups of containers when
+we cut a release, in which case the source of gcr.io/google_containers/kubectl
+would become that automated process.
+
+```pod.json``` is provided as an example of packaging kubectl as a sidecar
+container, and to help you verify that kubectl works correctly in
+this configuration.
+
+A possible reason why you would want to do this is to use ```kubectl proxy``` as
+a drop-in replacement for the old no-auth KUBERNETES_RO service. The other
+containers in your pod will find the proxy apparently serving on localhost.
+
+
+[![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/examples/kubectl-container/README.md?pixel)]()

kubectl-container/pod.json

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+{
+  "kind": "Pod",
+  "apiVersion": "v1beta3",
+  "metadata": {
+    "name": "kubectl-tester"
+  },
+  "spec": {
+    "containers": [
+      {
+        "name": "bb",
+        "image": "gcr.io/google_containers/busybox",
+        "command": [
+          "sh", "-c", "sleep 5; wget -O - ${KUBERNETES_RO_SERVICE_HOST}:${KUBERNETES_RO_SERVICE_PORT}/api/v1beta3/pods/; sleep 10000"
+        ],
+        "ports": [
+          {
+            "containerPort": 8080,
+            "protocol": "TCP"
+          }
+        ],
+        "env": [
+          {
+            "name": "KUBERNETES_RO_SERVICE_HOST",
+            "value": "127.0.0.1"
+          },
+          {
+            "name": "KUBERNETES_RO_SERVICE_PORT",
+            "value": "8001"
+          }
+        ],
+        "volumeMounts": [
+          {
+            "name": "test-volume",
+            "mountPath": "/mount/test-volume"
+          }
+        ]
+      },
+      {
+        "name": "kubectl",
+        "image": "gcr.io/google_containers/kubectl:v0.18.0-120-gaeb4ac55ad12b1-dirty",
+        "imagePullPolicy": "Always",
+        "args": [
+          "proxy", "-p", "8001"
+        ]
+      }
+    ],
+    "volumes": [
+      {
+        "name": "test-volume",
+        "emptyDir": {}
+      }
+    ]
+  }
+}