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/errno_mapping_test.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/errno_mapping.h"
+
+#include <errno.h>
+#include <stddef.h>
+
+#include <string>
+
+#include "common/status_test_macros.h"
+#include "gtest/gtest.h"
+
+namespace cdc_ft {
+namespace {
+
+// Errno value that is hopefully not defined on any OS.
+const int kUndefinedErrno = 999123;
+
+TEST(ErrnoMappingTest, ErrnoToCanonicalCode) {
+  EXPECT_EQ(ErrnoToCanonicalCode(0), absl::StatusCode::kOk);
+
+  // Spot-check a few errno values.
+  EXPECT_EQ(ErrnoToCanonicalCode(EINVAL), absl::StatusCode::kInvalidArgument);
+  EXPECT_EQ(ErrnoToCanonicalCode(ENOENT), absl::StatusCode::kNotFound);
+  EXPECT_EQ(ErrnoToCanonicalCode(kUndefinedErrno), absl::StatusCode::kUnknown);
+}
+
+TEST(ErrnoMappingTest, ErrnoToCanonicalStatus) {
+  EXPECT_OK(ErrnoToCanonicalStatus(0, ""));
+
+  // Spot-check a few errno values.
+  EXPECT_ERROR_MSG(InvalidArgument, "test0",
+                   ErrnoToCanonicalStatus(EINVAL, "test0"));
+  EXPECT_ERROR_MSG(NotFound, "test1", ErrnoToCanonicalStatus(ENOENT, "test1"));
+
+  // Apparently errno 999 is known not to be defined.
+  EXPECT_ERROR_MSG(Unknown, "test2",
+                   ErrnoToCanonicalStatus(kUndefinedErrno, "test2"));
+}
+
+}  // namespace
+}  // namespace cdc_ft