CrowdAnki
Plugin for Anki SRS designed to facilitate cooperation
...Providing you with the ability to automatically maintain a history of edits for your decks. My goal here is to provide a user-friendly description of collaboration workflow. In order to do that, I looked through multiple GUI git clients. For our purposes here, I think GitHub Desktop is the best choice (as the most user-friendly client that works). There is one problem with GitHub Desktop, though - it doesn't have a Linux version. Which makes me particularly sad, as I use Linux as my main OS.