public async Task <Stream> ReadFileContentsAsync(SystemFilepath systemPath)
        {
            var(dirname, basename) = systemPath.Split();
            var directory = directoryFactory.Open(dirname);

            return(await directory.ReadFileAsync(basename));
        }
 public async Task WriteFileContentsAsync(SystemFilepath systemPath, Stream contents)
 {
     var(dirname, basename) = systemPath.Split();
     var directory = directoryFactory.Open(dirname);
     await directory.WriteFileAsync(basename, contents);
 }