I think a tool like that could be very useful! The main issue with basing it off of Git commits is that there is no guarantee that the last commit with a given version is actually a good version. Consider the case where a-1.0 depends on b-1.0 and b is updated to b-2.0 in a commit so that a is not compatible with b-2.0. Even though a-1.0 is still around, it's not going to work until we update it to a-2.0, so you need some more complex constaint solving on top of your commits to figure out what works.

I would prefer doing it based on the 6-month release channels, so you get multiple version for every 6 months. You end up with some gaps between versions, but also have more guarantees everything actually works together. Basically "nix search" with multiple channels.

I actually had to do something similar with GHC versions for a project of mine. It turns out you can run Nixpkgs all the way back to the first release in 13.10 (LC_ALL=C is needed). Obviously not that long ago right now, but it should continue to work as time goes on & give us 10+ years.

https://gist.github.com/matthewbauer/ecdb665f84b7f6100f3f6e3...