migrates system shell

modules/hosts/dnsc-machine/default.nix

@@ -6,7 +6,11 @@ in
   flake.nixosConfigurations.dnsc-machine = inputs.nixpkgs.lib.nixosSystem {
     system = "x86_64-linux";
     modules = with config.flake.modules.nixos; [
+      # Modules
       base
+      shell
+
+      # Machine-specific configuration
       {
         imports = [ ./_hardware-configuration.nix ];
         networking.hostName = hostname;

modules/shell/default.nix

@@ -0,0 +1,18 @@
+{
+  ...
+}:
+{
+  flake.modules.nixos.shell =
+    { pkgs, ... }:
+    {
+      programs.fish.enable = true;
+      users.defaultUserShell = pkgs.fish;
+    };
+
+  flake.modules.darwin.shell =
+    { pkgs, ... }:
+    {
+      programs.fish.enable = true;
+      users.defaultUserShell = pkgs.fish;
+    };
+}