Tampermonkey / Greasemonkey script to fill the GitHub PR review summary based on the resolution chosen.

Fill the GitHub PR Review Summary.js

// ==UserScript==
// @name         Auto-fill GitHub PR Review Summary
// @namespace    http://jacksonc.com/
// @version      0.1
// @description  Fill the GitHub PR review summary based on the resolution chosen.
// @author       Jackson Cooper <jackson@jacksonc.com>
// @match        https://github.com/*/*/pull/*/files
// @grant        none
// ==/UserScript==

(function() {
  'use strict';

  // Map review resolution (radio button value) to review summaries.
  var resolutionSummaries = {
    'approve': 'Code approved :shipit:',
    'reject': 'Code reviewed, a few comments to look at.'
  };

  // Review summary `<textarea>`.
  var reviewSummaryTextArea = document.querySelector('#pull_request_review_body');

  // Add a `click` handler for the review summary radio buttons.
  var reviewRadios =  document.querySelectorAll('[type=radio][name^=pull_request_review]');
  Array.prototype.map.call(reviewRadios, function(reviewRadio) {
    reviewRadio.addEventListener('click', function(event) {
      var radioValue = event.currentTarget.value;
      if (radioValue in resolutionSummaries) {
        reviewSummaryTextArea.value = resolutionSummaries[radioValue];
      }
    });
  });
})();