anchor.diff:  { config, pkgs, ... }:
   
  -let
  -  snapshot = import (builtins.fetchGit {
  -    name = "nixpkgs-snapshot-2020-04-08";
  -    url = https://github.com/nixos/nixpkgs/;
  -    rev = "f1090bdaf85581c4e9e1fecfcc30f30bbf7a04d6";
  -  }) {
  -    config = config.nixpkgs.config;
  -  };
  -in
   {
     nixpkgs.overlays = [
       (import (builtins.fetchTarball {
  
positive.code:     python3Packages.youtube-dl
      ripgrep
      sloccount
      snapshot.page
      sshuttle
      stow
      tealdeer
  
negative.code:     tig
      universal-ctags
      unrar
      unstable.page
      unzip
      usbutils
      wget
  