Process diagram handling

does anybody know what is the best way to handle one process diagram (or more than one) when there are multiple people editing it?
For example take a basic situation in a project where you have to deliver some processes and there is more than one person editing the diagrams. So you have to take care of “synchronizing” the diagrams if you want to have the latest version available.
In IBM BPM there is some sort of support for “concurrent editing” and all of the diagrams are saved in Process designer.
But here in modeler, there is no such option.
So what is the best approach when you have to manage multiple diagrams and you have to share it with multiple people?
We were considering “cloud” approach but this would create duplicates due to 2 users editing one diagram at the same time.
Also, we don’t want to use Cawemo because of its lack of “properties” panel.

Thanks for any advice.

@lhofer87 do both users have to edit “collaboratively”?

How about using Git repositories?