docs: private static String getRelativePathForPath(final String relativePath, final String sep) {
          final StringTokenizer tokenizer = new StringTokenizer(relativePath.replace(WINDOWS_SEPARATOR, UNIX_SEPARATOR), UNIX_SEPARATOR);
          final StringBuilder buffer = new StringBuilder();
          if (tokenizer.countTokens() == 1) {
              return null;
          } else {
              while(tokenizer.countTokens() > 1) {
                  tokenizer.nextToken();
                  buffer.append("..");
                  buffer.append(sep);
              }
              return buffer.toString();
          }
      }