code: public static File getRelativePath(final File relativePath) {
          final String p = getRelativePathForPath(relativePath.getPath(), File.separator);
          return p != null ? new File(p) : null;
      }
docs: Get relative path to base path.
  
  <p>For {@code foo/bar/baz.txt} return {@code ../../}</p>
  
  @param relativePath relative path
  @return relative path to base path, {@code null} if reference path was a single file