Refined GitHub is a browser extension for Chrome and Firefox “that simplifies the GitHub interface and adds useful features”. The nice list of additions includes URL Condensing (pictured above) and Markdown preservation when copying comments (pictured below).
The extension is also able to add a few extra views, filters, and links (such as linking to issue references from the code view); but what I even like most of all is Refined GitHub’s goal:
Our hope is that GitHub will notice and implement some of these much needed improvements. So if you like any of these improvements, please email GitHub support about doing it.
The goal of Refined GitHub is to make itself obsolete.