To browse the CVS repository online and view the complete history of any file in the repository.
For Mesa see http://freedesktop.org/cgi-bin/viewcvs.cgi/mesa/
For DRI see http://freedesktop.org/cgi-bin/viewcvs.cgi/dri/
See CVS, ?CvsPolicy, and CvsBranches for more information on using the CVS repositories.