## Summary
This fixes an extremely subtle bug in `pip install --reinstall`, whereby
if you depend on `setuptools` at the top level, we end up uninstalling
it after resolving, which breaks some cached state. If we have
`--reinstall`, we need to reset that cached state between resolving and
installing.
## Test Plan
Running `pip install --reinstall` with:
```txt
setuptools
devpi @ e334eb4dc9/devpi-2.2.0.tar.gz
```
Fails on `main`, but passes.
Separate branch for rebasing #677 onto main because i don't trust the
rebase enough to force push.
Closes#677.
---
If you install `black` from PyPI, then `-e ../black`, we need to
uninstall the existing `black`. This sounds simple, but that in turn
requires that we _know_ `-e ../black` maps to the package `black`, so
that we can mark it for uninstallation in the install plan. This, in
turn, means that we need to build editable dependencies prior to the
install plan.
This is just a bunch of reorganization to fix that specific bug
(installing multiple versions of `black` if you run through the above
workflow): we now run through the list of editables upfront, mark those
that are already installed, build those that aren't, and then ensure
that `InstallPlan` correctly removes those that need to be removed, etc.
Closes#676.
Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>
