Add nix-output-monitor

Use nix-output-monitor for things like my rebuilds

home/modules/baseline/xonsh_footer.xsh

@@ -1,6 +1,6 @@
-# vim: set ft=python :
+# vim: set ft=xonsh :
 
-from tempfile import NamedTemporaryFile
+from tempfile import NamedTemporaryFile, TemporaryDirectory
 
 def bw_unlock():
     """Unlocks the BitWarden CLI and adds the resulting session code to the
@@ -48,7 +48,7 @@ aliases['glrestart'] = _glrestart
 
 def _cfetch(args):
     bw_unlock()
-    $CIRCLECI_CLI_TOKEN=$(bw get password CircleCI) 
+    $CIRCLECI_CLI_TOKEN=$(bw get password CircleCI)
     compass workspace exec bazel run src/go/compass.com/tools/circleci_results_cache/fetch/cmd/fetch:fetch
 aliases['cfetch'] = _cfetch
 
@@ -59,10 +59,18 @@ aliases['aws_creds'] = _aws_creds
 
 def _rebuild(args):
     system = uname()
+    hostname = system.nodename
     if system.sysname == 'Darwin':
         darwin-rebuild --flake ~/.config/darwin switch
     else:
-        sudo nixos-rebuild switch
+        with TemporaryDirectory() as td:
+            pushd @(td)
+            import platform
+            nom build f"/etc/nixos#nixosConfigurations.{hostname}.config.build.toplevel"
+            if g`result`:
+                nvd diff /run/current-system result
+                sudo result/bin/switch-to-configuration switch
+            popd
 aliases['rebuild'] = _rebuild
 
 def _yaml2json(args, stdin=None, stdout=None):