We just discussed how to best make sure that any pre- or post-deployment tasks required by some core changes get done. We agreed on the following:

If a change you submit to gerrit needs some pre- or post-deployment task to be performed (e.g. applying a database patch, changing a setting, purging some cache, etc), mention this in the commit message, using the DEPLOYMENT keyword (at the start of a line starting a new paragraph). E.g.:

DEPLOYMENT: frob the xyzzy when deploying this change!

I have written a brief deployment checklist that also reflects this new convention:

https://meta.wikimedia.org/wiki/Wikidata/Deployment

Please extend/modify as appropriate.

-- daniel