refactor overlays

overlays/default.nix

@@ -0,0 +1,20 @@
+# https://nixos.wiki/wiki/Overlays
+{ inputs, ... }:
+{
+  additions = final: _prev: import ../pkgs final.pkgs;
+
+  modifications = final: prev: {
+    # example = prev.example.overrideAttrs (oldAttrs: rec {
+    # ...
+    # });
+  };
+
+  # When applied, the unstable nixpkgs set (declared in the flake inputs) will
+  # be accessible through 'pkgs.unstable'
+  stable-packages = final: _prev: {
+    nixos-stable = import inputs.nixpkgs-stable {
+      system = final.system;
+      config.allowUnfree = true;
+    };
+  };
+}