factor out do_append in prep for delta subcommands

configuration.nix

@@ -0,0 +1,36 @@
+{ pkgs, modulesPath, ... }:
+
+{
+  imports = [
+    ./dynamic.nix
+    ./dynamic-options.nix
+    "${modulesPath}/profiles/qemu-guest.nix"
+  ];
+
+  dynamicism.for.gotosocial.enable = true;
+
+  # Just an example system.
+  users.mutableUsers = false;
+  users.users.root = {
+    password = "root";
+  };
+
+  services.openssh = {
+    enable = true;
+    settings = {
+      PermitRootLogin = "yes";
+    };
+  };
+
+  environment.shellAliases = {
+    ls = "eza --long --header --group --group-directories-first --classify --binary";
+  };
+
+  environment.systemPackages = with pkgs; [
+    eza
+    fd
+    ripgrep
+  ];
+
+  system.stateVersion = "25.11";
+}