How to make logstash-forwarder treat files from svn as updated not as rotated

I'm monitoring files which are periodically updated from SVN with logstash-forwarder, and I observed that logstash-forwarder treats them as rotated files and starts pushing them from beginning, even if only one line was added. This generates huge amount of traffic in our pipeline, and we have problems with that.
Is there any way to make logstash-forwarder to forward only newly added lines in that files?