docs: def freeze(dest_dir, opt):
      """Iterates over the Secretfile looking for secrets to freeze"""
      tmp_dir = ensure_tmpdir()
      dest_prefix = "%s/dest" % tmp_dir
      ensure_dir(dest_dir)
      ensure_dir(dest_prefix)
      config = get_secretfile(opt)
      Context.load(config, opt) \
             .freeze(dest_prefix)
      zip_filename = freeze_archive(tmp_dir, dest_prefix)
      ice_file = freeze_encrypt(dest_dir, zip_filename, config, opt)
      shutil.rmtree(tmp_dir)
      LOG.debug("Generated file is %s", ice_file)