Releasing the former Stadia file transfer tools

The tools allow efficient and fast synchronization of large directory
trees from a Windows workstation to a Linux target machine.

cdc_rsync* support efficient copy of files by using content-defined
chunking (CDC) to identify chunks within files that can be reused.

asset_stream_manager + cdc_fuse_fs support efficient streaming of a
local directory to a remote virtual file system based on FUSE. It also
employs CDC to identify and reuse unchanged data chunks.

cdc_fuse_fs/config_stream_client.h

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2022 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.
+ */
+
+#ifndef CDC_FUSE_FS_CONFIG_STREAM_CLIENT_H_
+#define CDC_FUSE_FS_CONFIG_STREAM_CLIENT_H_
+
+#include <memory>
+
+#include "absl/status/status.h"
+#include "grpcpp/grpcpp.h"
+#include "manifest/manifest_proto_defs.h"
+#include "proto/asset_stream_service.grpc.pb.h"
+
+namespace grpc_impl {
+class Channel;
+}
+
+namespace cdc_ft {
+
+class ManifestIdReader;
+
+class ConfigStreamClient {
+ public:
+  // |instance| is the id of the gamelet.
+  // |channel| is a gRPC channel to use.
+  ConfigStreamClient(std::string instance,
+                     std::shared_ptr<grpc::Channel> channel);
+  ~ConfigStreamClient();
+
+  // Sends a request to get a stream of manifest id updates. |callback| is
+  // called from a background thread for every manifest id received.
+  // Returns immediately without waiting for the first manifest id.
+  absl::Status StartListeningToManifestUpdates(
+      std::function<absl::Status(const ContentIdProto&)> callback);
+
+  // Sends a message to indicate that the |manifest_id| was received and FUSE
+  // has been updated to use the new manifest.
+  absl::Status SendManifestAck(ContentIdProto manifest_id);
+
+  // Stops listening for manifest updates.
+  void Shutdown();
+
+ private:
+  using ConfigStreamService = proto::ConfigStreamService;
+
+  const std::string instance_;
+  const std::unique_ptr<ConfigStreamService::Stub> stub_;
+
+  std::unique_ptr<ManifestIdReader> read_client_;
+};
+
+}  // namespace cdc_ft
+
+#endif  // CDC_FUSE_FS_CONFIG_STREAM_CLIENT_H_