Hi,
I want to check if https://gerrit.wikimedia.org/r/157836/ is live on dewp.
So I would get MediaWiki core's SHA1 from http://de.wikipedia.org/w/api.php?action=query&meta=siteinfo, extract the extension name from the Gerrit page, look at core's extensions/$EXTENSION SHA1 for the $VERSION_SHA1 and see if in the extension's repository $CHANGE_SHA1 is a par- ent of $EXTENSION_SHA1.
That sounds simple, but like work. Has someone done that already? (Web tools are welcome as well.)
Tim