As described in T115432: Get MW_CONFIG_FILE from env to facilitate virtual hosting, we could do something similar to prepend a settings file at /docker/DockerSettings.php, this could be useful for setting up config like T246942.
The file could also be a useful place to take environment variables defined in .env or in docker-compose.override.yml and translate them to MediaWiki config variables.
Change 582498 had a related patch set uploaded (by Kosta Harlan; owner: Kosta Harlan):
[releng/dev-images@master] Provide support for setting default configuration in dev image
Change 582499 had a related patch set uploaded (by Kosta Harlan; owner: Kosta Harlan):
[mediawiki/core@master] Allow setting MW_CONFIG_FILE via environment variable
The convention for this, as established by the PlatformSettings RFC (T182020) is for the MW provider (in this case the dev container) to create a one-line LocalSettings.php file that explicitly includes any shared or prepended settings from wherever they are kept.
Would that work here?
I wrote in the patch that I'd rather have one less step, but if the patch is rejected then we can work around that either with a LocalSettings.php that requires /docker/DockerSettings.php or with includes/PlatformSettings.php
Change 582499 abandoned by Kosta Harlan:
Allow setting MW_CONFIG_FILE via environment variable
Reason:
per comments
Change 582498 merged by Brennen Bearnes:
[releng/dev-images@master] Provide support for setting default configuration in dev image
Note that 582498: Provide support for setting default configuration in dev image was deployed along with 584111: Add install script to work around shell issues.