Reasonably efficient interwiki template transclusion

by Peter Potrowl for Wikimedia Foundation

The aim is to be able to include templates from another wiki on the WikiMedia Foundation wikis. This functionality has been requested since 2004 and has already been added to MediaWiki but is *not* enabled on WMF wikis because of performance problems. A bug report (#9890) opened in 2007 describes a solution to those problems, but it needs "a substantial amount of code" and someone doing it. That's what I propose to do.