Ember Data Snapshot and how to detect changes?

I'm writing my own adapter/serializer. In order to send data to backend, I have to detect changes in DS.Snapshot and original Ember object. For ordinary attributes, it is possible to changedAttributes() but I did not found a way how to detect changes in hasMany relations.

I can detect new relation using snapshot.hasMany('foo') and changedAttributes(). But this approach is not able to find deleted relations.