split overlays off

cfg/winter/main.nix

@@ -1,4 +1,4 @@
-{ config, pkgs, ... }: {
+{ config, overlays, pkgs, ... }: {
   networking.hostName = "winter";
   system.stateVersion = "20.09";
 
@@ -16,18 +16,9 @@
       experimental-features = nix-command flakes
     '';
   };
-  nixpkgs.overlays = [
-    (self: super: {
-      polybar = super.polybar.override { i3Support = true; };
-      picom = super.picom.overrideAttrs(old: {
-        src = pkgs.fetchFromGitHub {
-          repo = "picom";
-          owner = "ibhagwan";
-          rev = "60eb00ce1b52aee46d343481d0530d5013ab850b";
-          sha256 = "1m17znhl42sa6ry31yiy05j5ql6razajzd6s3k2wz4c63rc2fd1w";
-        };
-      });
-    })
+  nixpkgs.overlays = with overlays; [
+    polybar
+    picom
   ];
   nixpkgs.config.allowUnfree = true;
 

flake.nix

@@ -5,17 +5,26 @@
     secrets = { url = "github:LavaDesu/flakes-secrets"; };
   };
 
-  outputs = { self, nixpkgs, secrets }: {
-    nixosConfigurations."winter" = nixpkgs.lib.nixosSystem {
-      system = "x86_64-linux";
-      modules = [
-        {
-          system.configurationRevision = nixpkgs.lib.mkIf (self ? rev) self.rev;
-          nix.registry.nixpkgs.flake = nixpkgs;
-        }
-        secrets.nixosModules.winter
-        ./cfg/winter/main.nix
-      ];
+  outputs = { self, nixpkgs, secrets }: with nixpkgs.lib;
+    let
+      base = {
+        system.configurationRevision = mkIf (self ? rev) self.rev;
+        nix.registry.nixpkgs.flake = nixpkgs;
+      };
+      overlays = {
+        picom = import ./overlays/picom.nix;
+        polybar = import ./overlays/polybar.nix;
+      };
+    in
+    {
+      nixosConfigurations."winter" = nixosSystem {
+        system = "x86_64-linux";
+        modules = [
+          base
+          secrets.nixosModules.winter
+          ./cfg/winter/main.nix
+        ];
+        specialArgs = { inherit overlays; };
+      };
     };
-  };
 }

overlays/picom.nix

@@ -0,0 +1,10 @@
+self: super: {
+  picom = super.picom.overrideAttrs(old: {
+    src = super.fetchFromGitHub {
+      repo = "picom";
+      owner = "ibhagwan";
+      rev = "60eb00ce1b52aee46d343481d0530d5013ab850b";
+      sha256 = "1m17znhl42sa6ry31yiy05j5ql6razajzd6s3k2wz4c63rc2fd1w";
+    };
+  });
+}

overlays/polybar.nix

@@ -0,0 +1,3 @@
+self: super: {
+  polybar = super.polybar.override { i3Support = true; };
+}