Very frustrating. I’ve spent the whole week trying to work around a bug that got pushed to nixpkgs. Here is what I am doing now.
I installed an old version of nix by sh <(curl https://nixos.org/releases/nix/nix-2.1.2/install)
I fetched an old version of nixpkgs (nixpkgs-18.09) and use that for nix-env( -f ~/projects/nixpkgs-18.09). I load nixops-1.6 from that and it still has a bug that was introduced well after the date of those versions. (Calling testing.nix without required argument ‘pkgs’). How can I be seeing the changes that introduced the bug? How can I get back to the version I was using last week before I took in updates?