docs: public static RuleKey parse(String s) {
      int semiColonPos = s.indexOf(':');
      Preconditions.checkArgument(semiColonPos > 0, "Invalid rule key: " + s);
      String key = s.substring(0, semiColonPos);
      String repo = s.substring(semiColonPos + 1);
      return RuleKey.of(key, repo);
    }