GitHub Squash and Merge PR fixer

user.js

// ==UserScript==
// @name         GitHub Squash and Merge PR fixer
// @namespace    https://github.com/
// @version      1.0
// @description  try to take over the world!
// @author       Adam Johnson
// @match        https://github.com/*
// @grant        all
// ==/UserScript==

(function () {

  'use strict'

  const strip = function(string) {
    return string.replace(/^\s+|\s+$/g, '')
  }

  const fixCommitInfo = function () {
    const commitTitle = document.querySelector('input[name=commit_title]'),
          commitMessage = document.querySelector('textarea[name=commit_message]')

    console.log('>> fired')

    if (!commitTitle || !commitMessage)
      return

    commitTitle.value = (
        strip(document.querySelector('.js-issue-title').textContent) +
        ' (' +
        document.querySelector('.gh-header-number').textContent +
        ')'
    )

    commitMessage.value = (
        document.querySelector('textarea[name="pull_request[body]"]').value
    )
  }

  document.addEventListener('DOMContentLoaded', fixCommitInfo)

})()