gistfile1.js

// Add a button to Collapse or Expand files in a Github PR
//
// See it in action: http://cl.ly/image/1r3q3d0d3b0p
//
// Install Tampermonkey and add this as a script

// ==UserScript==
// @name         Github PRs: Collapse/expand file
// @namespace    https://gist.github.com/micho/855b272d2f408f04729e
// @version      0.1
// @description  Add a button to expand or collapse files in PRs
// @author       You
// @match        https://github.com/*/pull/*/files
// @grant        none
// ==/UserScript==


$(function () {
    $(".js-conduit-openfile-check").remove();

    $(".file .actions").prepend(function () {
      $button = $('<a href="#" class="minibutton">Collapse</a>')
      $button.click(function (e) {
        e.preventDefault();
        $(this).parents(".file").find(".data").toggle()
        $(this).text($(this).text() == "Collapse" ? "Expand" : "Collapse");
      });
      $(this).find(".minibutton").after($button).after(" ");
    })
});