code: function filesPatch(oldFile, newFile, options) {
    let { diff, toFile } = utils;
    let opts = options || {};
  
    oldFile = toFile(oldFile, options);
    newFile = toFile(newFile, options);
  
    let nameA = oldFile.relative;
    let nameB = newFile.relative;
  
    let strA = oldFile.contents.toString();
    let strB = newFile.contents.toString();
  
    return diff.createTwoFilesPatch(nameA, nameB, strA, strB, opts.oldHeader, opts.newHeader, opts);
  }
docs: Create a unified diff patch. See [diff] for supported options
  @param {String} `oldFile` [vinyl] file representing the existing file.
  @param {Buffer} `newFile` [vinyl] file representing the proposed file.
  @param {Object} `options`