Updates to `29c48fb9f3daa11bd02794edd55060d0b01ee705` from the
`pubgrub-rs` dev branch. This lets us reduce the number of changes we've
made to PubGrub itself (now, only changing visibility to export a few
things from the `solver.rs` module).
This PR reverts #109 which is actually a performance _regression_ since
we need to iterate over a bunch of wheels that we could otherwise
entirely ignore.
Rather than constantly iterating over all files and testing their
compatibility with the current platform, just store wheels we can
actually consider in the solver cache.
## Summary
This PR enables the proof-of-concept resolver to backtrack by way of
using the `pubgrub-rs` crate.
Rather than using PubGrub as a _framework_ (implementing the
`DependencyProvider` trait, letting PubGrub call us), I've instead
copied over PubGrub's primary solver hook (which is only ~100 lines or
so) and modified it for our purposes (e.g., made it async).
There's a lot to improve here, but it's a start that will let us
understand PubGrub's appropriateness for this problem space. A few
observations:
- In simple cases, the resolver is slower than our current (naive)
resolver. I think it's just that the pipelining isn't as efficient as in
the naive case, where we can just stream package and version fetches
concurrently without any bottlenecks.
- A lot of the code here relates to bridging PubGrub with our own
abstractions -- so we need a `PubGrubPackage`, a `PubGrubVersion`, etc.
Charlie Marsh