Fix the `devenv up` configuration which was ignoring the config overrides. (#15854)

* Fix use of config override directory in `devenv up`

`--config-directory` is for the generate config script; `-c` is for usage

* Add homeserver config override directory to gitignore

* Newsfile

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>

---------

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>

.gitignore

@@ -34,6 +34,7 @@ __pycache__/
 /logs
 /media_store/
 /uploads
+/homeserver-config-overrides.d
 
 # For direnv users
 /.envrc

changelog.d/15854.misc

@@ -0,0 +1 @@
+Fix the `devenv up` configuration which was ignoring the config overrides.

flake.nix

@@ -178,7 +178,7 @@
                   EOF
                 '';
                 # Start synapse when `devenv up` is run.
-                processes.synapse.exec = "poetry run python -m synapse.app.homeserver -c homeserver.yaml --config-directory homeserver-config-overrides.d";
+                processes.synapse.exec = "poetry run python -m synapse.app.homeserver -c homeserver.yaml -c homeserver-config-overrides.d";
 
                 # Define the perl modules we require to run SyTest.
                 #