[[ https://gerrit.wikimedia.org/r/#/c/209615/ | Change I8c9a6a567 ]] moved the image files for project logos into the `operations/mediawiki-config` repository. Doing so allows us to set far future expires cache headers for these images. The impact of the change was bigger than I anticipated because it had social consequences which I did not fully understand.
* Communities use the ability to upload a new version for a local file to set a temporary logo to mark some occasion. With I8c9a6a567 deployed, admins are still able to override the logo, but only via a Common.css rule. This needs to be communicated. @gpaumier is taking care of that. (Thanks!)
* The use of Common.css hacks should be discouraged. Communities should follow the process described in [[ https://meta.wikimedia.org/wiki/Requesting_wiki_configuration_changes | meta:Requesting wiki configuration changes ]] instead, and we should make sure we respond to such requests promptly.
* The mapping of image files in the config repository to the Commons images from which they derive should be preserved. I propose to do that by having the Commons URL for each project's logo declared in a configuration file, and having a build script that (re-)populates the `project-logos` directory by retrieving each image from its canonical location and applying lossless image optimization.