revamped nix for scalability

overlays/default.nix

@@ -0,0 +1,23 @@
+# This file defines overlays
+{inputs, ...}: {
+  # This one brings our custom packages from the 'pkgs' directory
+  additions = final: _prev: import ../pkgs {pkgs = final;};
+
+  # This one contains whatever you want to overlay 
+  # You can change versions, add patches, set compilation flags, anything really. 
+  # https://nixos.wiki/wiki/Overlays 
+  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'
+  unstable-packages = final: _prev: {
+    unstable = import inputs.nixpkgs-unstable {
+      system = final.system;
+      config.allowUnfree = true;
+    };
+  };
+}