How can multiple designers, working on the same design project, stay in sync?

The designers I manage always struggle to collaborate when they are working on the same project, and this takes a toll on the total time required to complete the project.

Developers don't have this problem because of this wonderful tool called git. Is there a "designer" alternative for git?

OR; what are the best tools out there for designers to collaborate and stay in sync; with improved productivity when compared to passing files around.

Thanks!