code: function buildResolverOptions(options, base) {
    var pathFilter = options.pathFilter;
  
    options.basedir = base;
    options.pathFilter = function(info, resvPath, relativePath) {
      if (relativePath[0] !== '.') {
        relativePath = './' + relativePath;
      }
      var mappedPath;
      if (pathFilter) {
        mappedPath = pathFilter.apply(this, [info, resvPath, path.normalize(relativePath)]);
      }
      if (mappedPath) {
        return mappedPath;
      }
      return;
    };
    return options;
  }
docs: Loosely based on an operation found in browser-resolve