Actually, the file handling isn't specified in the spec.txt file. But since it "mostly works", without triggering a reload or other means of rotating logs, at least the debian package seems to assume the openLog-write-close cycle, and new log lines are correctly written to mainlog only, not mainlog.1 or older versions.
Most of the time, I don't see an open mainlog with lsof, so there seems to be some corner situation with mainlog being left open.
