@edolstra Is this OK?

No, because adding every file in every directory listed in NIX_PATH sounds like it could seriously pollute the set of expressions evaluated by nix, potentially adding expressions that are not intended to be package sources.

For example, with the NIX_PATH on NixOS, this adds every package in Nixpkgs as a nixos.* set, doubling evaluation time for nix search and creating ambiguity. It also adds files like nixos-config which is also not exactly elegant.

In short NIX_PATH is not intended for this. The current use of nixpkgs= is a placeholder to be replaced when we have a proper nix-channel replacement.