instant repl for system flake with nixpkgs, use system nixpkgs for nix commands

hosts/default.nix

@@ -13,7 +13,7 @@ let
         usr = { inherit utils; };
         util = utils;
         nixosPersistence = "${impermanence}/nixos.nix";
-        nixpkgsFlake = nixpkgs;
+        inputs = inputs;
       };
 
       modules =

profiles/core.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, util, nixpkgsFlake, ... }:
+{ config, lib, pkgs, util, inputs, ... }:
 let
   inherit (util) pkgBin;
   inherit (lib) fileContents mkIf;
@@ -86,10 +86,25 @@ in
 
           myip =
             "${pkgs.dnsutils}/bin/dig +short myip.opendns.com @208.67.222.222 2>&1";
+
+          sys-repl =
+            "source /etc/set-environment && ${nixBin} repl ${./..}/repl.nix";
         };
     };
 
-  nix = {
+  nix =
+    let
+      flakes = lib.filterAttrs (name: value: value ? outputs) inputs;
+
+      nixPath = lib.mapAttrsToList
+        (name: _: "${name}=${inputs.${name}}")
+        flakes;
+
+      registry = builtins.mapAttrs
+        (name: v: { flake = v; })
+        flakes;
+    in
+    {
       package = pkgs.nixFlakes;
       autoOptimiseStore = true;
       optimise.automatic = true;
@@ -98,7 +113,8 @@ in
       extraOptions = ''
         experimental-features = nix-command flakes ca-references
       '';
-    registry.nixpkgs.flake = nixpkgsFlake;
+      nixPath = nixPath ++ [ "repl=${./..}/repl.nix" ];
+      inherit registry;
     };
 
   # security = {

repl.nix

@@ -0,0 +1,5 @@
+let
+  sysFlake = builtins.getFlake (toString ./.);
+  nixpkgs = import <nixpkgs> { };
+in
+{ inherit sysFlake; } // nixpkgs