github_ignore_whitespace.user.js

// ==UserScript==
// @name         GitHub Ignore Whitespace
// @namespace    http://spicewood.tech/
// @version      1.1
// @description  Add URL parameter to ignore whitespace in GitHub pull request reviews
// @author       Nimai C. Malle
// @match        https://github.com/*/*/pull/*
// @grant        none
// @downloadURL  https://gist.githubusercontent.com/NimaiMalle/9f1ddac7784632ba1b9b72f753dbcdf4/raw/github_ignore_whitespace.js?v=1.1
// ==/UserScript==

(function() {
    'use strict';

    const tabs = document.getElementsByClassName('tabnav-tab')
    for (let e of tabs) {
        if(e.nodeName==='A' && e.href.endsWith('files')) {
            e.href += '?utf8=✓&diff=split&w=1'
        }
    }

    const buttons = document.getElementsByClassName('btn')
    const filesRegex = /(.*\/files)(#.*|$)/
    var matches
    for (let e of buttons) {
        if(e.nodeName==='A' && (matches = e.href.match(filesRegex)) ) {
            e.href = matches[1] + '?utf8=✓&diff=split&w=1' + matches[2]
        }
    }

})();