The Ruby browser test running script has this enviable clause, https://phabricator.wikimedia.org/source/integration-config/browse/master/dockerfiles/quibble-stretch-bundle/mwselenium.sh$35-39
I want the same thing for selenium tests, so that MediaWiki configuration can be added before my test. In this specific case, for T190829 I want to add:
$wgEnableUploads = true;
Actually, the mwselenium.sh wouldn't quite work in our case, since the test is being run from mw-core so the base_dir is irrelevant to the extension repo where we need to adjust the LocalSettings.php. For the same reason, I'm not seeing an easy workaround where I inject settings from an extension script. If anything, I need to do this injection from the test case itself, which feels very wrong.