code: public static void unwrap(InputStream is, File outputDir) {
      unwrap(is, outputDir, IdentityNameMapper.INSTANCE);
    }
docs: Unwraps a ZIP file to the given directory shaving of root dir.
  If there are multiple root dirs or entries in the root of zip,
  ZipException is thrown.
  <p>
  The output directory must not be a file.
  
  @param is
  inputstream for ZIP file.
  @param outputDir
  output directory (created automatically if not found).