@Override
        void process(GlobToRegex converter, char c) {
          if (c == ']') {
            converter.appendBracketEnd();
            converter.popState();
          } else {
            converter.appendInBracket(c);
          }
        }
State inside [brackets], but not at the first character inside the brackets.
jimfs/src/main/java/com/google/common/jimfs/GlobToRegex.java