Since DeltaStreamer makes heavily use of file listing, if the source contains a lot of tiny files, this could quickly become a bottle neck. We need a way to delete/archive files once processed by DeltaStreamer.
It seems like the best way to reliably clean up the source is after DeltaSync commit the checkpoint successfully. We could add a new public method to Source e.g. `postCommit()` and invoke it after each successful commit