Allow limiting the scope of allow-newer

[mgsloan]

See haskell/cabal#2756 . We don't need to deal with allowing specific pkg1 <-> pkg2 constraints, though. Instead I think it's sufficient to just list which packages are allowed to differ from the constraints placed on them.

This is clearer than allow-newer: True about the reason for the allow-newer.

[mjrussell]

This is quite an old request but I was surprised to find out cabal.project supports this while stack does not. Any chance of getting this implemented?

[mgsloan]

Hey Matt! Agreed this would be much better than the blunt tool that is allow-newer: true. I think it would also be good to fix the naming - unfortunately allow-newer ignores all bounds, not just upper bounds.

[mjrussell]

Look at this small world :)

So maybe the way forward should be to create a new flag for this new behavior that is more clearly defined and eventually depreciate the existing allow-newer so users can transition to a more flexible and better named option?

[fosskers]

This would be great to have.

[recursion-ninja]

Maybe try to resolve this outstanding issue that was prematurely closed before perpetuating the poor semantics of allow-newer?

[isomorpheme]

It seems like this is solved now by the allow-newer-deps option? Though it is still labeled as experimental currently.

[mpilgrem]

I am closing this issue, as it was implemented in Stack 2.9.3. See also: #5910.