This article introduces two revision control tools - Git Gui and CodePlex. These tools allow you to check difference between two revisions of the source code, to publish large Small Basic source code with documentation and so on.
The first one is Git Gui for local revision control (and the interface to remote repository).
The second one is CodePlex created by Microsoft for remote revision control.
See detail in Small Basic: Revision Control.
Thank you Bob Irving for asking about GitHub (another remote revision control tool).