add GDrive provider support (#118)

* GDrive provider support
* More reliable basedir ownership
* Fix mimetype

vendor/cloud.google.com/go/authexample_test.go

@@ -0,0 +1,72 @@
+// Copyright 2016 Google LLC
+//
+// 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 cloud_test
+
+import (
+	"cloud.google.com/go/datastore"
+	"cloud.google.com/go/pubsub"
+	"golang.org/x/net/context"
+	"golang.org/x/oauth2/google"
+	"google.golang.org/api/option"
+)
+
+// Google Application Default Credentials is the recommended way to authorize
+// and authenticate clients.
+//
+// For information on how to create and obtain Application Default Credentials, see
+// https://developers.google.com/identity/protocols/application-default-credentials.
+func Example_applicationDefaultCredentials() {
+	client, err := datastore.NewClient(context.Background(), "project-id")
+	if err != nil {
+		// TODO: handle error.
+	}
+	_ = client // Use the client.
+}
+
+// You can use a file with credentials to authenticate and authorize, such as a JSON
+// key file associated with a Google service account. Service Account keys can be
+// created and downloaded from
+// https://console.developers.google.com/permissions/serviceaccounts.
+//
+// This example uses the Datastore client, but the same steps apply to
+// the other client libraries underneath this package.
+func Example_credentialsFile() {
+	client, err := datastore.NewClient(context.Background(),
+		"project-id", option.WithCredentialsFile("/path/to/service-account-key.json"))
+	if err != nil {
+		// TODO: handle error.
+	}
+	_ = client // Use the client.
+}
+
+// In some cases (for instance, you don't want to store secrets on disk), you can
+// create credentials from in-memory JSON and use the WithCredentials option.
+//
+// The google package in this example is at golang.org/x/oauth2/google.
+//
+// This example uses the PubSub client, but the same steps apply to
+// the other client libraries underneath this package.
+func Example_credentialsFromJSON() {
+	ctx := context.Background()
+	creds, err := google.CredentialsFromJSON(ctx, []byte("JSON creds"), pubsub.ScopePubSub)
+	if err != nil {
+		// TODO: handle error.
+	}
+	client, err := pubsub.NewClient(ctx, "project-id", option.WithCredentials(creds))
+	if err != nil {
+		// TODO: handle error.
+	}
+	_ = client // Use the client.
+}