mergemaster: "schg" flag for temproot/var/emtpy ??

[Rob Lahaye]

Hi,

I am trying to learn the buildworld and mergemaster process from the Handbook.

The handbook says:

[...]
To begin simply type mergemaster at your prompt, and watch it start going.
[..]

SO I did type mergemaster and all went well.

Decided then to remove the temproot directory, but failed!

# rm -rf /var/tmp/temproot
rm: /var/tmp/temproot/var/empty: Operation not permitted
rm: /var/tmp/temproot/var: Directory not empty
rm: /var/tmp/temproot/: Directory not empty

Took me a long while to figure out the /var/tmp/temproot/var/empty direcoty
has the schg flag set. Very, very confusing.
Is there any reason why it is like that?
If not, then do not create the empty directory with schg !!

Regards,
Rob.