Ask HN: What's the oldest publicly-available repo with different versions?

What is the oldest collection of code out there, including different versions of the same project, where someone could access it and compare the changes between versions to get a sense of what changed?

By publicly-available, I mean where it is made available for anyone who requested it to somehow access it (e.g. from the internet, from a library).

With "repo," I'm not imagining it using version-control software per se, just that it could be compared and clearly show some kind of iteration of the same piece of code.