Make sure that something added while Tart wasn't on didn't delete

So the problem now is that when you add something to a folder you sync in Tart, there are 2 possibilities:
 - If you update everything to make sure that nothing is deleted, because Tart wasn't aware of the change and doesn't use the --delete flag on start, you will get old files back and they won't ever be deleted.
 - If you do use the --delete flag, and you add something to your folder, start syncing than it will probably get deleted. Other way around, new files will get deleted from the server so you will never receive them.

So, make the above don't happen.