Add a command to check the system derivation actually changed

shell.nix

@@ -1,9 +1,17 @@
 { pkgs ? import <nixpkgs> { } }:
+let
+  nix-refactor = pkgs.writeShellScriptBin "nix-refactor" ''
+    origin=$(${pkgs.coreutils-full}/bin/readlink /run/current-system)
+    result=$(${pkgs.lib.getExe pkgs.nixos-rebuild} build && ${pkgs.coreutils-full}/bin/readlink result)
+    ${pkgs.diffutils}/bin/diff -q <(echo "$origin" ) <(echo "$result")
+  '';
+in
 pkgs.mkShell {
   name = "nixosbuildshell";
   nativeBuildInputs = with pkgs; [
     git
     nixFlakes
+    nix-refactor
     python3
     python310Packages.autopep8
     python310Packages.black
@@ -19,3 +27,4 @@ pkgs.mkShell {
     ''}/bin:$PATH
   '';
 }
+