docs: public static Optional<String> relativize(Path dir, Path file) {
      Path baseDir = dir.normalize();
      Path path = file.normalize();
      if (!path.startsWith(baseDir)) {
        return Optional.empty();
      }
      try {
        Path relativized = baseDir.relativize(path);
        return Optional.of(FilenameUtils.separatorsToUnix(relativized.toString()));
      } catch (IllegalArgumentException e) {
        return Optional.empty();
      }
    }