GDS has an absolute boat-load of repositories on GitHub, and no clear way to access or browse them.
One of those repositories, govuk-developers, is an ordered index to those repositories, allowing you to find exactly what you’re looking for. This is a static site generated with Middleman and served from Heroku, except that you need a GDS login to be able to access it (presumably for cost reasons).
In the description for that repo it says
This project is being rebuilt and is undergoing rapid change. but there haven’t been any changes for nearly a week, so I’ve forked it.
It’s now running in my Heroku account with no username and password (there’s a prompt, but just hit
<ENTER>), so you too can browse the GDS repos and docs in a useful way.