nix-shell with custom nix channel
In NixOS, there is an old world of Nix channels, environments, and paths, and a
new world of Nix flakes, inputs, and outputs. Today, after a long time, I needed
to run nix-shell -p foo
again, but it kept failing with an error stating that
the package could not be found, even though I could find it while searching the
stable and unstable channels.