duplicates:

• SR-3689 Persist editable state even when an editable package is no longer required

Issue Description:

If you edit a package that's in your dependency graph, then change another dependency (by pinning it to a different revision, or by editing it and changing what's checked out), such that the first dependency is no longer in your dependency graph, you now can't unedit the first dependency. SwiftPM gives an "error: The provided package was not found"

I'd expect you to be able to unedit it, though you then couldn't re-edit it as long as it wasn't in the dependency graph.

Steps to reproduce:

1. Check out vapor (git@github.com:vapor/vapor.git)
2. Check out the 2.0.0-alpha.7 tag
3. Run `swift package show-dependencies` to load the dependency graph
4. Run `swift package edit CTLS --branch test`
5. Run `swift package edit TLS --branch test`
6. Run `cd Packages/TLS && git checkout 2.0.0-alpha.2 && cd ../..`
7. Run `swift package unedit CTLS`