Implement upgrade feature

[XVilka]

Many years passed and people still struggle how to update all packages, like e.g. opam upgrade can.
There is even a workaround like:

cabal list --simple-output --installed | awk '{print $1}' | uniq | xargs -I {} cabal install {} --reinstall

(taken from https://stackoverflow.com/questions/6905163/whats-the-best-workaround-for-not-having-cabal-upgrade/6905267#6905267 )

Would be nice to finally have it. (Yes, I know about Stack, but it's still far from being widely used).

[hvr]

This may have made sense in the old-build paradigm, but it doesn't apply anymore in the nix-style local builds paradigm (where a world file doesn't make much sense anymore), where the package db (which is called a "nix-style store") is merely a binary cache. It's not a stateful pkg db you can "upgrade". Or did I misunderstand your suggestion?

See also http://cabal.readthedocs.io/en/latest/nix-local-build-overview.html

[23Skidoo]

Check out cabal outdated and #4831.

[gbaz]

closing as obsolete