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.

common/status.cc

@@ -0,0 +1,54 @@
+// 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.
+
+#include "common/status.h"
+
+#include "absl/strings/numbers.h"
+
+namespace cdc_ft {
+namespace {
+
+constexpr char kTagKey[] = "tag";
+
+absl::Cord TagToCord(Tag tag) {
+  return absl::Cord(std::to_string(static_cast<int>(tag)));
+}
+
+absl::optional<Tag> CordToTag(absl::optional<absl::Cord> cord) {
+  if (!cord.has_value()) return {};
+
+  int value;
+  absl::numbers_internal::safe_strto32_base(std::string(cord.value()), &value,
+                                            10);
+  return value >= 0 && value < static_cast<int>(Tag::kCount)
+             ? static_cast<Tag>(value)
+             : absl::optional<Tag>();
+}
+
+}  // namespace
+
+absl::Status SetTag(absl::Status status, Tag tag) {
+  status.SetPayload(kTagKey, TagToCord(tag));
+  return status;
+}
+
+bool HasTag(const absl::Status& status, Tag tag) {
+  return status.GetPayload(kTagKey) == TagToCord(tag);
+}
+
+absl::optional<Tag> GetTag(const absl::Status& status) {
+  return CordToTag(status.GetPayload(kTagKey));
+}
+
+}  // namespace cdc_ft