anchor.diff:      :l() {
           if [ ! -e .envrc ]; then
               echo 'use nix' > .envrc
  +            direnv edit .
           fi
  -        direnv allow
           eval "$(direnv hook zsh)"
       }
   
       :r() {
  -        direnv reload
  +        if [ -z "$IN_NIX_SHELL" ]; then
  +            eval "$(direnv hook zsh)"
  +        else
  +            direnv reload
  +        fi
  +    }
  +
  +    :a() {
  +        nix repl ''${@:-<nixpkgs>}
       }
   
       xi() {
  
positive.code: 
      otool() {
          ${pkgs.darwin.cctools}/bin/otool "$@"
      }
  
      pkgs() {
          nix repl ''${@:-<nixpkgs>}
      }
  
      aarch-build() {
  
negative.code:           esac
            EOF
          '';
  
        vim_configurable = super.vim_configurable.override {
          ftNixSupport = false;  # enable using a custom vim-nix
        };
      })
  
      (self: super: {
        # TODO: fix darwin build in nixpkgs.
        kitty = super.runCommandNoCC "kitty" {} ''
          mkdir -p $out/bin
          ln -s /Applications/Kitty.app/Contents/MacOS/kitty $out/bin
        '';
  
        vimPlugins = super.vimPlugins or {} // {
        };
      })
    ];
  
    services.khd.khdConfig = ''
      # modifier only mappings
  