release-merge-sanity-checker.user.js

// ==UserScript==
// @name         Release Merge Sanity Checker
// @version      1.0
// @description  :^)
// @author       ryanml
// @match        https://github.com/MetaMask/metamask-extension/pull/*
// @grant        none
// ==/UserScript==

(function() {
  // The final merge button isn't present in the initial DOM content, rather 
  // loaded in shortly after, so we have to wait for it
  const findMergeButton = async () => {
    return new Promise((resolve, _reject) => {
      let retries = 0
      const findButtonInterval = setInterval(() => {
        const mergeButton = document.querySelector('.hx_create-pr-button:enabled')
        if (mergeButton || retries === 500) {
          clearInterval(findButtonInterval)
          resolve(mergeButton)
        }
        retries++
      }, 10)
    })
  }

  const init = async () => {
    const branchName = document.querySelector('.head-ref')?.textContent
    if (branchName !== 'master-sync' &&
        !branchName?.match(/Version-v[0-9\.]{1,}/)) {
      return
    }

    const mergeButton = await findMergeButton()

    if (mergeButton?.classList.contains('btn-group-squash')) {
      mergeButton.onclick = (event) => {
        window.alert(
          'This looks like a release related PR, should you be merging this instead?'
        )
      }
    }
  }

  window.onload = () => {
    init()
  }
})();