warn-nixpkgs

Wrap nixpkgs, but emit a warning if this one is ever accessed.

The Nix world is gradually adopting flakes and moving toward a world where there are no longer nix-update-maintained channels. During that transition, it's nice to have system channels that still work, but emit a warning when they are accessed to alert the user of of a gap in their move-to-flakes.

This repo can be used as a drop-in replacement for the nixpkgs channel. This repo doesn't contain nixpkgs -- this is merely a thin wrapper. Configure the actual nixpkgs to forward to as a nixpkgs-warned channel.