docs: public static Path pathForFileInRoot(
              final File rootDir,
              final File file
      )
      {
          String filePath = file.getAbsolutePath();
          String rootPath = rootDir.getAbsolutePath();
          if (!filePath.startsWith(rootPath)) {
              throw new IllegalArgumentException("not a file in the root directory: " + file);
          }
          return pathForRelativeFilepath(filePath.substring(rootPath.length()));
      }