feat(/usr/local/bin/k): Install kubectl just-in-time

See https://github.com/jakepearson/k

Author: mboersma

README.md

@@ -27,6 +27,7 @@ creating [issues][] and submitting [pull requests][].
 * [helm][]: Kubernetes package manager
 * [jq][]: command-line JSON processor
 * [jwt][]: tool for creating and parsing JSON Web Tokens
+* [k][]: automatically run the correct version of `kubectl` every time
 * [kubectl][]: Kubernetes command-line client
 * [Packer][]: build automated machine images
 * [ruby][]: ruby scripting language
@@ -83,6 +84,7 @@ The latest deis/go-dev Docker image is available at:
 [issues]: https://github.com/deis/docker-go-dev/issues
 [jq]: https://stedolan.github.io/jq/
 [jwt]: https://github.com/dgrijalva/jwt-go
+[k]: https://github.com/jakepearson/k
 [kubectl]: https://kubernetes.io/docs/user-guide/kubectl-overview/
 [pull requests]: https://github.com/deis/docker-go-dev/pulls
 [Quay.io]: https://quay.io

rootfs/usr/local/bin/k

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+set +x
+
+KX_PATH="$HOME/.kx"
+mkdir -p "$KX_PATH/cache"
+
+case "$OSTYPE" in
+  *arwin*)
+    OS="darwin"
+    ;;
+  *in32* | *indows*)
+    OS="windows"
+    ;;
+  *)
+    OS="linux"
+esac
+
+# Attempt to load the server version from cache
+if [ ! -z "$KUBECONFIG" ]; then
+  if [ "$OS" == "darwin" ]; then
+    KUBECONFIG_HASH=$(echo "$KUBECONFIG" | shasum -a 256 | cut -c1-5)
+  else
+    KUBECONFIG_HASH=$(echo "$KUBECONFIG" | sha256sum | cut -c1-5)
+  fi
+  VERSION_CACHE_FILE="$KX_PATH/cache/$KUBECONFIG_HASH"
+  TARGET_VERSION=$(cat "$VERSION_CACHE_FILE" 2> /dev/null)
+fi
+
+# Get the server version from the server if not cached
+if [ -z "$TARGET_VERSION" ]; then
+  TARGET_VERSION=$(kubectl version -o json 2>/dev/null | jq -r '.serverVersion.gitVersion')
+fi
+
+# Default to kubectl v1.10.12 if TARGET_VERSION was unset and `kubectl version` failed
+if [ "$TARGET_VERSION" == "null" ]; then
+  TARGET_VERSION=v1.10.12
+fi
+
+# Fill the cache if possible
+if [ ! -z "$KUBECONFIG" ]; then
+  echo "$TARGET_VERSION" > "$VERSION_CACHE_FILE"
+fi
+
+TARGET=$KX_PATH/kubectl-$TARGET_VERSION
+
+if [ ! -f $TARGET ]; then
+  cd "$KX_PATH"
+  echo "Downloading kubectl $TARGET_VERSION..."
+  curl -sLO "https://storage.googleapis.com/kubernetes-release/release/$TARGET_VERSION/bin/$OS/amd64/kubectl"
+  mv $KX_PATH/kubectl $TARGET
+  chmod +x $TARGET
+fi
+
+$TARGET "$@"