overlay rework

overlays/default.nix

@@ -0,0 +1,16 @@
+{ inputs }:
+let
+  dir = builtins.readDir ./.;
+  overlayNames = builtins.sort builtins.lessThan (builtins.filter (
+    name:
+      name != "default.nix"
+      && dir.${name} == "regular"
+      && builtins.match ".*\\.nix" name != null
+  ) (builtins.attrNames dir));
+  overlayPath = name:
+    builtins.toPath "${builtins.toString ./.}/${name}";
+  loadOverlay = name:
+    let
+      overlayModule = import (overlayPath name);
+    in overlayModule { inherit inputs; };
+in map loadOverlay overlayNames