new driver: kubernetes

Tested with `kind` and GKE.

Note: "nodes" shown in `docker buildx ls` are unrelated to Kubernetes "nodes".
Probably buildx should come up with an alternative term.

Usage:

  $ kind create cluster
  $ export KUBECONFIG="$(kind get kubeconfig-path --name="kind")"

  $ docker buildx create --driver kubernetes --driver-opt replicas=3 --use
  $ docker buildx build -t foo --load .

`--load` loads the image into the local Docker.

Driver opts:

  - `image=IMAGE` - Sets the container image to be used for running buildkit.
  - `namespace=NS` - Sets the Kubernetes namespace. Defaults to the current namespace.
  - `replicas=N` - Sets the number of `Pod` replicas. Defaults to 1.
  - `rootless=(true|false)` - Run the container as a non-root user without `securityContext.privileged`. Defaults to false.
  - `loadbalance=(sticky|random)` - Load-balancing strategy. If set to "sticky", the pod is chosen using the hash of the context path. Defaults to "sticky"

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

vendor/google.golang.org/appengine/internal/identity_vm.go

@@ -0,0 +1,101 @@
+// Copyright 2011 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+
+package internal
+
+import (
+	"net/http"
+	"os"
+
+	netcontext "golang.org/x/net/context"
+)
+
+// These functions are implementations of the wrapper functions
+// in ../appengine/identity.go. See that file for commentary.
+
+const (
+	hDefaultVersionHostname = "X-AppEngine-Default-Version-Hostname"
+	hRequestLogId           = "X-AppEngine-Request-Log-Id"
+	hDatacenter             = "X-AppEngine-Datacenter"
+)
+
+func ctxHeaders(ctx netcontext.Context) http.Header {
+	c := fromContext(ctx)
+	if c == nil {
+		return nil
+	}
+	return c.Request().Header
+}
+
+func DefaultVersionHostname(ctx netcontext.Context) string {
+	return ctxHeaders(ctx).Get(hDefaultVersionHostname)
+}
+
+func RequestID(ctx netcontext.Context) string {
+	return ctxHeaders(ctx).Get(hRequestLogId)
+}
+
+func Datacenter(ctx netcontext.Context) string {
+	return ctxHeaders(ctx).Get(hDatacenter)
+}
+
+func ServerSoftware() string {
+	// TODO(dsymonds): Remove fallback when we've verified this.
+	if s := os.Getenv("SERVER_SOFTWARE"); s != "" {
+		return s
+	}
+	return "Google App Engine/1.x.x"
+}
+
+// TODO(dsymonds): Remove the metadata fetches.
+
+func ModuleName(_ netcontext.Context) string {
+	if s := os.Getenv("GAE_MODULE_NAME"); s != "" {
+		return s
+	}
+	return string(mustGetMetadata("instance/attributes/gae_backend_name"))
+}
+
+func VersionID(_ netcontext.Context) string {
+	if s1, s2 := os.Getenv("GAE_MODULE_VERSION"), os.Getenv("GAE_MINOR_VERSION"); s1 != "" && s2 != "" {
+		return s1 + "." + s2
+	}
+	return string(mustGetMetadata("instance/attributes/gae_backend_version")) + "." + string(mustGetMetadata("instance/attributes/gae_backend_minor_version"))
+}
+
+func InstanceID() string {
+	if s := os.Getenv("GAE_MODULE_INSTANCE"); s != "" {
+		return s
+	}
+	return string(mustGetMetadata("instance/attributes/gae_backend_instance"))
+}
+
+func partitionlessAppID() string {
+	// gae_project has everything except the partition prefix.
+	appID := os.Getenv("GAE_LONG_APP_ID")
+	if appID == "" {
+		appID = string(mustGetMetadata("instance/attributes/gae_project"))
+	}
+	return appID
+}
+
+func fullyQualifiedAppID(_ netcontext.Context) string {
+	appID := partitionlessAppID()
+
+	part := os.Getenv("GAE_PARTITION")
+	if part == "" {
+		part = string(mustGetMetadata("instance/attributes/gae_partition"))
+	}
+
+	if part != "" {
+		appID = part + "~" + appID
+	}
+	return appID
+}
+
+func IsDevAppServer() bool {
+	return os.Getenv("RUN_WITH_DEVAPPSERVER") != ""
+}