clean up fenix and add direnv

modules/devtools.nix

@@ -1,9 +1,5 @@
 { pkgs, inputs, ... }: {
 
-  nixpkgs.overlays = [
-    inputs.fenix.overlay
-    inputs.emacs-overlay.overlay
-  ];
   environment.systemPackages = with pkgs; [
     # general
     cmake
@@ -11,16 +7,27 @@
     binutils
     clang
     clang-tools
+    direnv
+    (nix-direnv.override  { enableFlakes = true; })
     # rust
-    (inputs.fenix.packages."x86_64-linux".stable.withComponents [
-      "cargo"
-      "clippy"
-      "rust-src"
-      "rustc"
-      "rustfmt"
-    ])
-    rust-analyzer-nightly
+    (inputs.fenix.packages."x86_64-linux".stable.toolchain)
     # nix
     rnix-lsp
   ];
+
+  ## direnv
+  programs.bash.interactiveShellInit = ''
+    eval "$(direnv hook bash)"
+  '';
+  programs.zsh.interactiveShellInit = ''
+    eval "$(direnv hook zsh)"
+  '';
+  # nix options for derivations to persist garbage collection
+  nix.extraOptions = ''
+    keep-outputs = true
+    keep-derivations = true
+  '';
+  environment.pathsToLink = [
+    "/share/nix-direnv"
+  ];
 }

modules/graphical.nix

@@ -58,8 +58,8 @@
     allowBitmaps = true;
     useEmbeddedBitmaps = true;
     defaultFonts.emoji = [
-      "Twitter Color Emoji"
       "Noto Color Emoji"
+      "Twitter Color Emoji"
     ];
   };