The default way to consume nixpkgs is through channels which today does not involve git. And a nixpkgs git checkout is over 1GB (my .git dir is currently sitting at 1.4GB on this machine). So that's not great.
> If you maintain such a "database", you'd have to explicitly state version info for the dependencies of every package.
I don't know what you mean. If I say "I want git v2.10.0" I don't care about dependencies; whatever nixpkgs tarball I download that has that will have the dependencies too. There will be a whole range of nixpkgs tarballs that contain the requested git version of course, but with such a database I could also say "find me a channel tarball that contains both git v2.10.0 and some-dependency v7.23" if I want that particular combination (assuming the two coexisted in the same nixpkgs at some point).
> For a particular version of a package, the versions of the dependencies it's compatible with are those that are present in the same commits.
This is true of downloading a nixpkgs channel tarball too.
> Also, to maintain package building scripts in a database outside of git would require either making 1 script per package that builds every version of that package ever.
I don't know what you mean by this either.
> Re-reading your comment thought, I think you're talking about pre-built packages.
No I'm not.
What I'm talking about is just any time hydra builds a channel, it can run a script that collects the pname/version combination for every derivation in nixpkgs (or at least, every searchable derivation; we probably don't need to collect this from all the invisible helper derivations). This can then be appended to a database from the previous version, such that we end up with this information for every single tarball.
In fact, this is pretty much exactly what you'd do for git, except you'd build it incrementally rather than running a script that processes the entire git history from scratch (which is pretty much building it incrementally for every commit).
