docs: protected void pruneEmptyDirectories( File directory,
                                            File removeable ) {
          assert directory != null;
          assert removeable != null;
          if (directory.equals(removeable)) {
              return;
          }
  
          assert isAncestor(directory, removeable);
          while (!removeable.equals(directory)) {
              if (removeable.exists()) {
                  // It exists, so try to delete it...
                  if (!removeable.delete()) {
                      // Couldn't delete it, so stop
                      return;
                  }
              }
              removeable = removeable.getParentFile();
          }
      }