[opensuse-buildservice] How to clean up /srv/obs/sources?

Hi, I just noticed that I have ~6GB in repositories (binary and source rpms/deps), but my obs uses ~600GB on disk... Then I found the culprit. It's the /srv/obs/sources folder: 6.4G repos 521G sources Okay, now how to get rid of the useless old stuff? My disk is again filling up... :-( -- With best regards, Carsten Hoeger