anchor.diff:  with lib;
   
   let
  +  cfg = config.nixpkgs;
  +
     isConfig = x:
       builtins.isAttrs x || builtins.isFunction x;
   
  
positive.code:         takes as an argument the <emphasis>original</emphasis> Nixpkgs.
          The first argument should be used for finding dependencies, and
          the second should be used for overriding recipes.
        '';
      };
  
  
negative.code:         If unset, it defaults to the platform type of your host system.
          Specifying this option is useful when doing distributed
          multi-platform deployment, or when building virtual machines.
  
          Ignored when <code>nixpkgs.pkgs</code> is set.
        '';
      };
    };
  
    config = {
      _module.args = {
        pkgs = cfg.pkgs;
        pkgs_i686 = cfg.pkgs.pkgsi686Linux;
      };
    };
  }
  