treewide: set system.nixos.revision

nix/configurations/installer.nix

@@ -4,6 +4,9 @@
 # figured out an elegant (enough) way to do it while keeping my secrets
 # encrypted.
 #
+let
+  sources = import ../../npins;
+in
 {
   pkgs,
   lib,
@@ -41,6 +44,15 @@
     ];
   };
 
+  system.nixos =
+    let
+      rev = lib.substring 0 8 sources.nixpkgs.revision;
+    in
+    {
+      versionSuffix = "-git:${rev}";
+      revision = rev;
+    };
+
   isoImage.squashfsCompression = "zstd -Xcompression-level 3";
 
   environment.systemPackages = [