Hi everyone,
Yesterday on IRC, I suggested that I should start checking in the safer portions of the extensionless-files branch, so as to make the eventual merge of the feature easier. Tim suggested that I put together a design doc and post that here for wider review first.
Here's the design doc: http://www.mediawiki.org/wiki/Requests_for_comment/Extensionless_files
The branch with the code in it is here: http://www.mediawiki.org/w/index.php?title=Special:Code/MediaWiki/path&p...
Ongoing discussion on this topic is in Bugzilla: https://bugzilla.wikimedia.org/show_bug.cgi?id=4421
Rob