code: function rewriteDest(dest, src, opts) {
    dest = utils.resolve(dest);
    if (opts.destBase) {
      dest = path.join(opts.destBase, dest);
    }
    if (opts.extDot || opts.hasOwnProperty('ext')) {
      dest = rewriteExt(dest, opts);
    }
    if (typeof opts.rename === 'function') {
      return opts.rename(dest, src, opts);
    }
    return dest;
  }
docs: Used when `mapDest` is not true