Added useful git tools

roles/nixpkgs-dev.nix

@@ -12,6 +12,7 @@
 
   environment = {
     systemPackages = with pkgs; [
+      bat                      #  A cat clone with syntax highlighting & Git integration
       cabal2nix                # Convert Cabal files into Nix build instructions
       nix-prefetch-github      # Prefetch sources from github
       nix-prefetch-git         # Prefetch sources from git
@@ -20,6 +21,7 @@
       nodePackages.node2nix    # Generate Nix expressions to build NPM packages
       nox                      # Tools to make Nix nicer
       sqlite                   # To query the nixpkgs sqlite database
+      tig                      # Text-mode interface for git
     ];
   };