wip: feat: Just use straight.el...

Every Nixy solution I could find or conceive had too many points spread across
these various facets:
  - Flimsy (emacsWithPackagesFromUsePackage)
  - Inelegant (builtins.exec, manual listings)
  - Inflexible (emacsWithPackagesFromUsePackage)
  - Otherwise unergonomic (everything }:D)

Straight.el is sufficiently declarative, flexible, and Nix-friendly without
blindly bowing down to the imperialist NixOS user.  Now, Convenience and
ergonomics shan't be forsaken for the dogma that is total Nixation.

users/crumb/programs/emacs.nix

@@ -17,8 +17,8 @@ let
 
   # Create a new instance of nixpkgs with emacs-overlay applied. This is a
   # little unorthodox, but we do it
-  #   1. for the sake of organisation — For pure aesthetics and a clean codebase, I want
-  #      everything Emacs to stay in this file;
+  #   1. for the sake of organisation — For pure aesthetics and a clean
+  #      codebase, I want everything Emacs to stay in this file;
   #   2. and, there's simply no need to leak emacs-overlay's packages into the
   #      global nixpkgs instance when nothing else is using it!
   pkgs' = import inputs.nixpkgs {
@@ -26,20 +26,32 @@ let
     overlays = [ emacs-overlay ];
   };
 
-  my-emacs = pkgs'.emacsWithPackagesFromUsePackage {
-    config = ./emacs/init.el;
-    defaultInitFile = false;
-    package = emacsPackage;
-    alwaysEnsure = true;
-  };
-in {
-  programs.emacs = {
-    enable = true;
-    package = my-emacs;
-    extraConfig = ''
-      (load (file-name-concat "${emacsConfigDir}" "init"))
+  straightBaseDir = "${config.xdg.dataHome}/straight";
+
+  emacsWrapper = pkgs.symlinkJoin {
+    name = "emacs-wrapper";
+    paths = [ emacsPackage ];
+    buildInputs = [ pkgs.makeWrapper ];
+    postBuild = ''
+      for i in $out/bin/emacs-*; do
+        wrapProgram "$i" \
+          --add-flags "--init-directory \"${emacsConfigDir}\""
+      done
     '';
   };
+in {
+  sydnix.impermanence.cache.directories = [ straightBaseDir ];
+  home.packages = [ emacsWrapper ];
+
+  home.sessionVariables.EMACS_STRAIGHT_BASE_DIR = straightBaseDir;
+
+  # programs.emacs = {
+  #   enable = true;
+  #   package = emacsPackage;
+  #   # extraConfig = ''
+  #   #   (load (file-name-concat "${emacsConfigDir}" "init"))
+  #   # '';
+  # };
 
   services.emacs = {
     enable = true;