meta: add build info to motd / system label, remove /etc/haccfiles

flake.nix

@@ -58,9 +58,9 @@
         system = "x86_64-linux";
         modules = [
           ./parsons/configuration.nix
+          ./modules/buildinfo.nix
           sops-nix.nixosModules.sops
           { nixpkgs.pkgs = pkgs; }
-          { environment.etc."haccfiles".source = self.outPath; }
         ];
         specialArgs = {
           sources = inputs;

modules/buildinfo.nix

@@ -0,0 +1,30 @@
+{ config, lib, pkgs, sources, ... }:
+
+let
+  self = sources.self;
+  slice = string: start: length: with lib;
+    strings.concatStrings
+      (lists.take length
+        (lists.drop start
+          (strings.stringToCharacters string)));
+
+  formatDate = date:
+    let
+      year = slice date 0 4;
+      month = slice date 4 2;
+      day = slice date 6 2;
+      hour = slice date 8 2;
+      minute = slice date 10 2;
+      second = slice date 12 2;
+    in
+      "${year}-${month}-${day} ${hour}:${minute}:${second} UTC";
+in
+{
+  system.nixos.label = "${config.system.nixos.release}-haccfiles-${self.shortRev or self.dirtyShortRev}";
+  users.motd = ''
+    Welcome to ${config.networking.hostName}, running NixOS ${config.system.nixos.release}!
+    Built from haccfiles ${self.rev or self.dirtyRev}.
+    Last commit was at ${formatDate self.lastModifiedDate}.
+    ${if self ? dirtyRev then "\nPlease remember to commit your changes.\n" else ""}
+  '';
+}