emacs: only rebuild straight-env when necessary

home/profiles/emacs/default.nix

@@ -10,9 +10,41 @@ let
     doom = "~/.emacs.d/bin/doom";
   };
 in {
-  programs.doom-emacs = {
+  programs.doom-emacs = rec {
     enable = true;
     doomPrivateDir = pkgs.callPackage ./doom.d { };
+
+    # Only init/packages so we only rebuild when those change.
+    doomPackageDir = let
+      filteredPath = builtins.path {
+        path = doomPrivateDir;
+        name = "doom-private-dir-filtered";
+        filter = path: type:
+          # builtins.elem (baseNameOf path) [ "init.el" "packages.el" "modules" ];
+          let
+            relPath =
+              lib.removePrefix (toString doomPrivateDir + "/") (toString path);
+            regexes = [ "init.el" "packages.el" "modules(/.*)?" ];
+          in lib.any (re: builtins.match re relPath != null) regexes;
+      };
+    in pkgs.linkFarm "doom-packages-dir" [
+      {
+        name = "init.el";
+        path = "${filteredPath}/init.el";
+      }
+      {
+        name = "packages.el";
+        path = "${filteredPath}/packages.el";
+      }
+      {
+        name = "modules";
+        path = "${filteredPath}/modules";
+      }
+      {
+        name = "config.el";
+        path = pkgs.emptyFile;
+      }
+    ];
   };
 
   home.packages = with pkgs;

home/profiles/emacs/doom.d/packages.el

@@ -65,3 +65,5 @@
 (package! monky)
 
 (package! writefreely)
+
+(package! mastodon)