refactor

nixos/common/global/nix.nix

@@ -0,0 +1,27 @@
+{ config, inputs, lib, ... }:
+
+{
+  nix = {
+    gc = {
+      # Automatically run the garbage collector an a specified time.
+      automatic = true;
+      dates = "weekly";
+      options = "--delete-older-than 30d";
+    };
+
+    # This will add each flake input as a registry
+    # To make nix commands consistent with your flake
+    registry = lib.mapAttrs (_: value: { flake = value; }) inputs;
+
+    # This will additionally add your inputs to the system's legacy channels
+    # Making legacy nix commands consistent as well, awesome!
+    nixPath = lib.mapAttrsToList (key: value: "${key}=${value.to.path}") config.nix.registry;
+
+    settings = {
+      # Enable flakes and new 'nix' command
+      experimental-features = "nix-command flakes";
+      # Deduplicate and optimize nix store
+      auto-optimise-store = true;
+    };
+  };
+}