Last modified: 2014-08-30 15:29:48 UTC
There are obsolete references to MessagesXx.php/MessagesEn.php in includes/DefaultSettings.php, includes/cache/LocalisationCache.php, includes/installer/Installer.php, and languages/Language.php .
These includes an exception thrown at runtime (as well as documentation). They should all be updated to accurately reflect the current behavior.
Some of these may not be obsolete, since MessagesEn.php is still used for other purposes, but e.g. https://git.wikimedia.org/blob/mediawiki%2Fcore.git/134f34e04f5ca339a57c0bf13f07488376333f37/includes%2Fcache%2FLocalisationCache.php#L449 threw when I had a cache issue, and MessagesEn.php was certainly not missing (nor do I think it was related).