github-show-all-files.user.js

// ==UserScript==
// @name         Github - Show all files
// @namespace    https://github.com/Koopzington
// @version      0.1
// @description  Shows all files by default
// @author       koopzington@gmail.com
// @match        https://github.com/*
// @downloadURL  https://gist.github.com/Koopzington/8c374786511a37ebfac47cfd2db958c6/raw/github-show-all-files.user.js
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    // Also execute this script if content is getting loaded via pjax
    document.addEventListener("pjax:complete", function () {
        showAllFiles();
    });
    showAllFiles();

    function showAllFiles() {
        let btn = document.querySelector('.btn-truncate-file-list')
        if (btn) {
            btn.click();
        }
    }
})();