Hey, is there a way to keep another backup that is only incrementing the contacts instead of syncing to the latest state?
No, not with DAVdroid. DAVdroid is a sync tool to keep your local device in sync with the server.
It once deleted all my existing contacts on the server instead of downloading them to the phone.
How did this happen? Are you absolutely sure? DAVdroid only sends a DELETE request to the server when a contact has explicitly been deleted in the Contacts app, i.e. the raw contact’s DELETED flag is set.
In a earlier version of davdroid you could set up that nothing would be deleted.
The first version of DAVdroid which supports “force read-only” is 1.9.4, which has just been released.