On Mon, Nov 8, 2010 at 7:17 AM, Markus Krötzsch
<markus(a)semantic-mediawiki.org> wrote:
The proposed backward compatibility page says
that trunk extensions
are only compatible with the current MW version. This implies that it is not
possible to cleanly develop an extension that supports multiple MW versions
in trunk at all: since branches are copies of an earlier state of the trunk,
the proposed guidelines entail that branches are also compatible with only
one version of MediaWiki.
Actually, what it says is:
"Extensions are branched along with MediaWiki, so trunk extensions
only have to support current trunk MediaWiki. However, per #General
principles, don't break support for old MediaWiki versions unless the
compatibility code is causing actual quantifiable problems, because
it's nice if users can get the extra features or bug fixes of trunk
extensions even if they're still using old MediaWiki. Some extensions'
maintainers deliberately maintain compatibility with old MediaWiki
versions, and their wishes should be respected in all cases."
The last sentence answers your question. The phrase "have to" in the
first sentence means they don't have to support old releases, but they
can if their maintainers want them to.
Great, I overlooked this last part. +1 from me.
What remains of my email is the question how this "wish" is implemented
technically. Either one has to generally give up potentially problematic
updates on ./trunk/extensions, or there must be some record of each
extension's compatibility wish to determine which extensions an update
should be applied to.
-- Markus