dentritic refactor

options/hostname-check.ulu.nix

@@ -0,0 +1,23 @@
+{ ... }:
+{
+  commonModules.hostname-assert =
+    { config, lib, ... }:
+    {
+      options.elars.expectedHostName = lib.mkOption {
+        type = lib.types.nullOr lib.types.str;
+        default = null;
+        description = "host filename must match networking.hostName.";
+      };
+
+      config.assertions = lib.singleton {
+        assertion =
+          config.elars.expectedHostName == null
+          || config.networking.hostName == config.elars.expectedHostName;
+        message = ''
+          syntax: hostname assertion failed:
+           expected (filename) : ${toString config.elars.expectedHostName}
+           real (networking)  : ${toString config.networking.hostName}
+        '';
+      };
+    };
+}