Bugfix: `nix-env -iA` completion failed when defexpr contained duplicates
Bugfix: `nix-env -iA` completion failed when defexpr contained duplicates

This can realistically happen if both the user and root have the 'unstable'
channel for instance

PS: Not sure why, but the search actually works when ~/.nix-defexpr contains
symlink cycles too..

PS: We don't search hidden directories

spwhitt/nix-zsh-completions