We use SVN. I personally prefer it to Git because I find the operations are simpler and more explicit... and like Git it is a full version control with merging code and marking revisions. In previous years we stored the repository on our team laptop and networked all the programmers' laptops with it using a router. This gave us full access to the history at competition on our team laptop if needed and in addition we make a back up to a flash drive of every version of code that is downloaded to the robot during the competition. This has been a saving grace a couple of times when someone in the pit moved the programming laptop and thought they didn't touch anything.
However, since this year's communications strategy lends itself to using Wifi, we have moved our repository to the cloud on SourceForge which works well with SVN. This will provide further flexibility for student programmers to grab updates at home and still fulfills our other needs. We will still be using the flashdrive backup occasionally during build season and most definitely everytime we deploy code at competition. There is nothing worse than not being sure what source code was used to generate the executable that is currently sitting on the robot.
