You can trace changes to lines in a file and discover how parts of the file evolved over time.
When viewing a file on your enterprise, you can press the "y" key to update the URL to a permalink to the exact version of the file you see.
GitHub AE supports rendering and diffing in a number of non-code file formats.
All GitHub docs are open source. See something that's wrong or unclear? Submit a pull request.
Or, learn how to contribute.