Apache error log contains refernce to /usr/bin/diff

Hi folks,

this is one of those that is impossible to search Google for. I searched here and didn't find anyone else asking about it.

I occasionally get the following in my Apache 2.2 error logs on my Ubuntu 64bit 10.04LTS server.

/usr/bin/diff: `-5' option is obsolete; use `-C 5'
/usr/bin/diff: Try `/usr/bin/diff --help' for more information.

There's nothing in syslog to correspond with the time (figured by the timestamp for the previous entry - I just happened to have been running tail on the logs) or any mention of diff.

Has anyone else seen this? Could it be caused by a remote rsync?

Thanks everyone.

Mike