astal: fix update script

pkgs/development/libraries/astal/source.nix

@@ -3,31 +3,34 @@
   nix-update-script,
   fetchFromGitHub,
 }:
-(fetchFromGitHub {
-  owner = "Aylur";
-  repo = "astal";
-  rev = "dc0e5d37abe9424c53dcbd2506a4886ffee6296e";
-  hash = "sha256-5WgfJAeBpxiKbTR/gJvxrGYfqQRge5aUDcGKmU1YZ1Q=";
-}).overrideAttrs
-  (
-    final: prev: {
-      name = "${final.pname}-${final.version}"; # fetchFromGitHub already defines name
-      pname = "astal-source";
-      version = "0-unstable-2025-03-21";
+let
+  originalDrv = fetchFromGitHub {
+    owner = "Aylur";
+    repo = "astal";
+    rev = "dc0e5d37abe9424c53dcbd2506a4886ffee6296e";
+    hash = "sha256-5WgfJAeBpxiKbTR/gJvxrGYfqQRge5aUDcGKmU1YZ1Q=";
+  };
+in
+originalDrv.overrideAttrs (
+  final: prev: {
+    name = "${final.pname}-${final.version}"; # fetchFromGitHub already defines name
+    pname = "astal-source";
+    version = "0-unstable-2025-03-21";
 
-      meta = prev.meta // {
-        description = "Building blocks for creating custom desktop shells (source)";
-        longDescription = ''
-          Please don't use this package directly, use one of subpackages in
-          `astal` namespace. This package is just a `fetchFromGitHub`, which is
-          reused between all subpackages.
-        '';
-        maintainers = with lib.maintainers; [ perchun ];
-        platforms = lib.platforms.linux;
-      };
+    meta = prev.meta // {
+      description = "Building blocks for creating custom desktop shells (source)";
+      longDescription = ''
+        Please don't use this package directly, use one of subpackages in
+        `astal` namespace. This package is just a `fetchFromGitHub`, which is
+        reused between all subpackages.
+      '';
+      maintainers = with lib.maintainers; [ perchun ];
+      platforms = lib.platforms.linux;
+    };
 
-      passthru = prev.passthru // {
-        updateScript = nix-update-script { extraArgs = [ "--version=branch" ]; };
-      };
-    }
-  )
+    passthru = prev.passthru // {
+      updateScript = nix-update-script { extraArgs = [ "--version=branch" ]; };
+      src = originalDrv;
+    };
+  }
+)