We branch and tag extensions along with versions of
MediaWiki, so the
code found at
http://svn.wikimedia.org/svnroot/mediawiki/tags/REL1_15_5/extensions/
is supposed to work with MW 1.15.5. However, this assumes that the
trunk version of each extension worked with the trunk version of MW at
the time of the branch point, which is not always the case and is the
responsibility of the extension maintainer. Versioned releases can
also be downloaded through ExtensionDistributor at
mediawiki.org,
although ED breaks all the time and we've been getting lots of
questions in #mediawiki from people whose wiki broke because they
installed the trunk version of ParserFunctions (downloaded through ED)
with MediaWiki 1.15.
Though branches, tags, and the extension distributor exist, in reality none
of them come even close to solving the problem.
The issue is, none of these things allow an extension author to properly
match a version of an extension to a version of MediaWiki. The solution I
take is to always have my extension useable in the trunk version, and
backwards compatible to as many versions of MediaWiki as possible.
This is a problem we need to solve. This is one of the things that makes
upgrading MediaWiki a crap shoot.
V/r,
Ryan Lane