If you develop MediaWiki core, or work on extensions that the Wikimedia Foundation deploys, you should prepare for your development workflow to switch on the weekend of March 3rd. Instead of Subversion and the Code Review tool at mediawiki.org, we will be using Git and Gerrit.
Summary: https://blog.wikimedia.org/2012/02/15/wikimedia-engineering-moving-from-subv...
Affected projects: https://www.mediawiki.org/wiki/Git/Conversion#Affected_development_projects
If you work on an extension that the Wikimedia Foundation does not use, or on a non-MediaWiki project hosted at svn.wikimedia.org, you have more time to decide. Talk it over with your community and decide whether you would like to move to Git immediately, move to Git sometime over the next several months, or move to another hosting provider sometime before mid-2013. We would like to gradually migrate all projects currently on Wikimedia's Subversion repository so that we can make all of svn.wikimedia.org read-only by the middle of 2013, and thus only have to support one source control infrastructure.
New workflow instructions, open issues, docs, etc.: https://www.mediawiki.org/wiki/Git
Thank you. (Please feel free to forward this to affected communities.)