buildbot and subversion on ubuntu 12.04

[Mike Dewhirst]

I'm setting up on Ubuntu server for the first time. Ex-OpenSuSE.

Not knowing any better, I got buildbot and subversion working well 
together last night with buildbot running as user "build".

This morning it wouldn't work.

When I investigated, the ownership of /var/lib/buildbot and sub-dirs 
thereof had mysteriously changed from build:build to buildbot:buildbot.

Why is it so?

Thanks

Mike