vendors/tempy.js/hasBraceExpansion
    function hasBraceExpansion(pattern) {
      const openingBraceIndex = pattern.indexOf("{");
      if (openingBraceIndex === -1) {
        return false;
      }
      const closingBraceIndex = pattern.indexOf("}", openingBraceIndex + 1);
      if (closingBraceIndex === -1) {
        return false;
      }
      const braceContent = pattern.slice(openingBraceIndex, closingBraceIndex);
      return BRACE_EXPANSION_SEPARATORS_RE.test(braceContent);
    }