stdlib: add GKE support

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

stdlib/gcp/gke/gke.cue

@@ -0,0 +1,84 @@
+package gke
+
+import (
+	"dagger.io/dagger/op"
+	"dagger.io/gcp"
+)
+
+// KubeConfig config outputs a valid kube-auth-config for kubectl client
+#KubeConfig: {
+	// GCP Config
+	config: gcp.#Config
+
+	// GKE cluster name
+	clusterName: string
+
+	// Kubectl version
+	version: *"v1.19.9" | string
+
+	// kubeconfig is the generated kube configuration file
+	kubeconfig: {
+		// FIXME There is a problem with dagger.#Secret type
+		string
+
+		#up: [
+			op.#Load & {
+				from: gcp.#GCloud & {
+					"config": config
+				}
+			},
+
+			op.#WriteFile & {
+				dest:    "/entrypoint.sh"
+				content: #Code
+			},
+
+			op.#Exec & {
+				always: true
+				args: [
+					"/bin/bash",
+					"--noprofile",
+					"--norc",
+					"-eo",
+					"pipefail",
+					"/entrypoint.sh",
+				]
+				env: {
+					GKE_CLUSTER:     clusterName
+					KUBECTL_VERSION: version
+				}
+				mount: "/cache/bin": "cache"
+			},
+			op.#Export & {
+				source: "/kubeconfig"
+				format: "string"
+			},
+		]
+	}
+}
+
+#Code: #"""
+	[ -e /cache/bin/kubectl ] || {
+	   curl -sfL https://dl.k8s.io/${KUBECTL_VERSION}/bin/linux/amd64/kubectl -o /cache/bin/kubectl \
+	    && chmod +x /cache/bin/kubectl
+	}
+
+	export KUBECONFIG=/kubeconfig
+	export PATH="$PATH:/cache/bin"
+
+	# Generate a kube configiration
+	gcloud -q container clusters get-credentials "$GKE_CLUSTER"
+
+	# Figure out the kubernetes username
+	CONTEXT="$(kubectl config current-context)"
+	USER="$(kubectl config view -o json | \
+	    jq -r ".contexts[] | select(.name==\"$CONTEXT\") | .context.user")"
+
+	# Grab a kubernetes access token
+	ACCESS_TOKEN="$(gcloud -q config config-helper --format json --min-expiry 1h | \
+	    jq -r .credential.access_token)"
+
+	# Remove the user config and replace it with the token
+	kubectl config unset "users.${USER}"
+	kubectl config set-credentials "$USER" --token "$ACCESS_TOKEN"
+	"""#