Collapsable Diffs and Linked Branches (GitHub)

Adds a toggle to collapse diffs in GitHub's pull request and commit diff interfaces
As of 2016-03-16. See the latest version.
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// ==UserScript==
// @name        Collapsable Diffs and Linked Branches (GitHub)
// @namespace   chriskim06
// @description Adds a toggle to collapse diffs in GitHub's pull request and commit diff interfaces
// @include     https://github.com/*
// @require     http://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js
// @version     1.4.4
// @grant       none
// @locale      en
// ==/UserScript==
 
this.$ = this.jQuery = jQuery.noConflict(true);
 
$(function() {
 
  function collapsable() {
    if ($('#files').length) {
      // Add buttons in each header to allow folding the diff
      var expanded = 'M0 5l6 6 6-6H0z';
      var collapsed = 'M0 14l6-6L0 2v12z';
      var diffs = $('#files').find('div[id^="diff-"]');
      diffs.each(function() {
        var diff = $(this);
        var info = diff.find('.file-info');
        if (!info.children().first().is('a')) {
          // If the button isn't there add it and add the event handler
          info.prepend(
            '<a class="octicon-btn custom-collapsable" href="javascript:void(0)">' +
              '<svg height="16" width="12" xmlns="http://www.w3.org/2000/svg">' +
                '<path d="' + expanded + '" />' +
              '</svg>' +
            '</a>'
          );
          diff.find('.octicon-btn.custom-collapsable').on('click', function() {
            // Toggle the visibility of the diff and the direction of the arrow
            var icon = $(this).find('path');
            diff.children('.data.highlight.blob-wrapper').toggle();
            icon.attr('d', (icon.attr('d') === collapsed) ? expanded : collapsed);
            var allButton = $('#diff-collapse-button');
            var visible = diffs.children('.data.highlight.blob-wrapper').is(':visible');
            allButton.attr('data-toggle-state', visible ? 'expanded' : 'collapsed');
            allButton.text(visible ? 'Collapse All' : 'Expand All');
          });
        }
      });
 
      var diffOptions = $('.diffbar-item.dropdown.js-menu-container');
      if (diffOptions.length && diffOptions.find('a').length === 2) {
        // Add an Expand/Collapse All button if its not there
        var blobs = diffs.children('.data.highlight.blob-wrapper');
        diffOptions.find('ul').append(
          '<a id="diff-collapse-button" ' +
            'class="dropdown-item" ' +
            'href="javascript:void(0)" ' +
            'data-toggle-state="' + (blobs.is(':visible') ? 'expanded' : 'collapsed') + '">' +
            (blobs.is(':visible') ? 'Collapse All' : 'Expand All') +
          '</a>'
        );
        $('#diff-collapse-button').on('click', function() {
          // Toggle the visibility of all diffs, directions of arrows, and the button
          var state = ($(this).attr('data-toggle-state') === 'expanded');
          if (state) {
            blobs.hide();
          } else {
            blobs.show();
          }
          $('.octicon-btn.custom-collapsable').find('path').attr('d', state ? collapsed : expanded);
          $(this).attr('data-toggle-state', state ? 'collapsed' : 'expanded');
          $(this).text(state ? 'Expand All' : 'Collapse All');
          diffOptions.removeClass('active');
        });
      }
    }
  }
 
  function makeLinks() {
    var head = $('#partial-discussion-header');
    if (head.length && head.find('.flex-table-item.flex-table-item-primary > a').length === 1) {
      // Turn the branches being compared into links if they aren't already
      var r = window.location.href.match(/(https:\/\/github\.com\/)([A-Za-z0-9_-]+\/([A-Za-z0-9_-]+))/);
      if (r) {
        $('span.commit-ref.current-branch').each(function() {
          var branch = $(this).text();
          if (branch.indexOf(':') === -1) {
            r[1] += r[2] + '/tree/' + branch;
          } else {
            r[1] += branch.split(':')[0] + '/' + r[3] + '/tree/' + branch.split(':')[1];
          }
          $(this).wrap('<a href="' + r[1] + '"></a>');
        });
      }
    }
  }
  
  makeLinks();
  collapsable();
 
  window.$(document).on('pjax:end pjax:complete', function() {
    makeLinks();
    collapsable();
  });
  
});