On September 22nd I started an initiative to document what extension authors should be doing when trying to support newer (and older!) versions of mediawiki. This culminated in
[1] http://www.mediawiki.org/wiki/Manual:Extension_support
Now that we have a new version coming out (1.18.0beta1, I would like to call core dev attention to two articles that need updating:
[2] http://www.mediawiki.org/wiki/Manual:Extension_support/1.18/ExtUpgrading
Is for extensions authors who have extensions in 1.17 and want to update them for 1.18. Please feel free to add anything you know of. While code samples for best-practices are encouraged, linking to manual pages where new documentation resides is the preferred method when possible.
[3] http://www.mediawiki.org/wiki/Manual:Extension_support/1.17/ExtDowngrading
Is for extension authors who are coding against 1.18, and want to support the large number of 1.17 already deployed who will take awhile to upgrade. A strong emphasis here would be on branching code that allows people to use the new "preferred" method while still retaining support for older methods (through the use of method_exists and the like). Code samples are more frequent here, but again please link to actual documentation for individual objects, methods, etc.
One advantage of having itemized lists like this is that extension authors don't have to dig through all the changelogs (which often just have a short summary and links to bug reports), and changes are more clearly communicated to the community of developers. People who have requirements for supporting older wikis also have clear instructions on how to best go about it, and our "upgrade" instructions of the future quickly become our "downgrade" instructions of the past.
Hopefully in the long run this will help communication between these two bodies.
Thanks, Olivier Finlay Beaton