message: Use @ as escape character of cache filenames
  Fixes
diff: @@ -224,9 +224,9 @@ void EnsureEndsInSlash(std::string& path) {
  std::string EscapeFileName(std::string path) {
  if (path.size() && path.back() == '/')
  path.pop_back();
  - std::replace(path.begin(), path.end(), '\\', '_');
  - std::replace(path.begin(), path.end(), '/', '_');
  - std::replace(path.begin(), path.end(), ':', '_');
  + std::replace(path.begin(), path.end(), '\\', '@');
  + std::replace(path.begin(), path.end(), '/', '@');
  + std::replace(path.begin(), path.end(), ':', '@');
  return path;
  }
  