Compare from commit

compareFromCommit-TamperMonkey.js

// ==UserScript==
// @name         compareFromCommit
// @namespace    http://buznik.net/
// @version      0.1.1
// @description  The script inserts a link to compare commits from the current commit in Github pull-request
// @author       Alex Buznik
// @include      /https:\/\/github.com\/(.*[^/])\/(.*[^/])\/pull\/(.*)/
// @downloadURL  https://gist.githubusercontent.com/beshur/e1398ff5e741308cd29476f75d612bdd/raw/compareFromCommit-TamperMonkey.js
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    let commitLinks = document.querySelectorAll('.commit-meta .commit-id')

    let getCompareLink = (href) => {
      return href.replace('/commits/', '/files/') + '..HEAD'
    }
    let createCompareEl = (href) => {
      let el = document.createElement('a')
      el.innerText = '⚖︎'
      el.title = 'Compare starting from this commit'
      el.className = 'compareFromCommit'
      el.style = `position: absolute;
        right: -19px;
        margin-top: 4px;
        font-size: 10px;`
      el.href = href
      return el
    }

    commitLinks.forEach(el => {
      let link = getCompareLink(el.href)
      let container = el.parentNode.parentNode
      container.insertBefore(createCompareEl(link), el.parentNode)
    })
})();

The script creates the link to compare commit in the Github pull-request starting from the current commit.
Useful when you have updated the pull-request and want to direct reviewers to that portion of code that's changed.
Inserts the scale icon next to the commit hash.

Please remember you need to click the commit, that is previous to the start of the range.