Extension:ExtensionDistributor

The ExtensionDistributor extension generates .tar.gz snapshots of extensions in the git repository and distributes them. It is intended for use on www.mediawiki.org. See Special:ExtensionDistributor to see how it works.

Installation
You'll need to set up some configuration for the extension to work. For Wikimedia's Gerrit instance, it would look like:

The Gerrit provider requires an independent tarball generator, the source code for the one running at extdist.wmflabs.org can be found here.