GitHub Lando linker

GitHub Lando linker.user.js

// ==UserScript==
// @name     GitHub Lando linker
// @version  1
// @author   Olivier Mehani <omehani@mozilla.com>
// @downloadURL https://gist.github.com/shtrom/20aeb11b6b6c07f9b392786b4d01067b
// @grant    none
// @match    https://github.com/mozilla-firefox/firefox/*
// @match    https://github.com/mozilla-conduit/lando/*
// @run-at   document-idle
// ==/UserScript==

const logName = "GreaseMonkey GLL";
let debugLog = function() {} ;
//debugLog = console.debug;

const buttonLabels = [
  "Squash and merge",
  "Merge pull request",
]

function updateMergeButton() {

    let xpath = document.evaluate(
     '//button//span[contains(text(), "Squash and merge") \
                  or contains(text(), "Merge pull request") \
                    ]/ancestor::button',
      document,
      null,
      XPathResult.ANY_UNORDERED_NODE_TYPE,
      null);
  
  	if (!xpath.singleNodeValue) {
      debugLog(logName + ": no button found");
      return;
    }
  
  	const mergeButton = xpath.singleNodeValue;
  
    // This is a Lando-supported repo. Disable in any case.
    mergeButton.disabled = true;
  
    xpath = document.evaluate(
  	  '//a[contains(text(), "View this pull request in Lando")]/@href',
      document,
      null,
      XPathResult.STRING_TYPE,
      null);
  
  	if (!xpath.stringValue) {
      console.warning(logName + ": no Lando URL found");
      return;
    }
  
  	const landoURL = xpath.stringValue;
  
    const landoButton = document.createElement("button");
  
    landoButton.classList = mergeButton.classList;
  
    landoButton.onclick= function() { window.open(landoURL); };
    landoButton.textContent = "View in Lando";
    landoButton.style.backgroundColor="orange";
    //landoButton.style.color="black";
  
    mergeButton.replaceWith(landoButton);
}

function callback (mutations) {
    updateMergeButton();
}

let observer = new MutationObserver(callback);
let observerOptions = {
    childList: true,
    subtree: true
};

updateMergeButton();

observer.observe(document.body, observerOptions);


console.info(logName + ": ready");