# Pastebin XteJTwQv
~/projects/nixpkgs emacsHead 8s
❯ nix-env -f . -i emacsHead
error: selector 'emacsHead' matches no derivations

~/projects/nixpkgs emacsHead 8s
❯ nix-env -f . -qaP 'emacs*'
emacs25    emacs-25.3
emacs      emacs-26.2
emacsHead  emacs-27