History of MediaWiki version control/gu
MediaWiki's source code has been hosted by a number of tools and technologies over the years.
CVS
MediaWiki's source code history began in SourceForge's CVS version control system. We started a project there before the names "MediaWiki" or "Wikimedia" were coined; thus the project name was "wikipedia". This project was used to host pre-MediaWiki wiki software (Magnus Manske's "phase 2"), and finally Lee Daniel Crocker's "phase 3" rewrite which came to be known as MediaWiki.
SVN
An extended outage of SourceForge's developer CVS service forced our hand to finally go ahead and set up our own source code repository as of April 1, 2006. That new repository used Subversion (Archived 2004-04-01 at the Wayback Machine), which was ever so slightly trendier than CVS but provided a pretty similar interface.
Between April 1, 2006 and May 31, 2007, the repository was hosted on Brion's offsite server at www.leuksman.com.
Between May 31, 2007 and October 23, 2010, the repository was hosted on host mayflower, a Wikimedia server in Amsterdam.
Between October 23, 2010 and November 2013, the repository was hosted on formey, in the Tampa data center.
After that, it was hosted on antimony.
git
In March 2012, conversion of the existing Subversion repository to Git was initiated and completed in the following weeks. Gerrit is used as a code review tool. On July 26th 2013, that entire Subversion repository went to read-only for all the projects it supported. It was eventually decommissioned completely in June 2015.
In 2020, it was announced that Wikimedia will be moving its code-hosting and code-review from gerrit to GitLab (still self-hosted).