Rsyncd has a temp dir feature that is undocumented

[ConstantinJean]

Hi,

Using rsync version 3.2.7, I stumbled upon a temp dir option in the rsyncd configuration.
If I set under a module the temp dir like so:

[data]
  path = /data
  temp dir = /.rsyncd_tmp

Provided that the /data/.rsyncd_tmp directory is created, transfers to the rsync module data will use /data/.rsyncd_tmp as a temporary directory during the transfer.

I see references to that option in the daemon-parm.txt file as well.

However, there is no reference to that feature in the man page rsyncd.conf.5

It seems to work fine so is that just missing documentation or should that feature not be used?