Path-based auth with svn+ssh

Hello list,

I would like to setup a repository that is *only* accessible over svn+ssh. I
follow
        
http://svnbook.red-bean.com/nightly/en/svn.serverconfig.svnserve.html#svn.serverconfig.svnserve.sshtricks

to setup public-key-based authentication and let all users share the same
account (using 'command="svnserver -t --tunnel-user=joe" JOES-KEY
joe@example.com' in .ssh/authorized_keys).

Everything works all right so far.

Now, and additionally, I would like to setup path-based authorization. I
uncomment the lines "[general]" and "authz-db = authz" in svnserve.conf, and
the file authz contains the following lines:

[repository:/trunk]
joe = rw

Trying to commit something to that repository yields:

svn: Commit failed (details follow):
svn: Authorization failed

Where is the problem? Have I exposed myself as noob? :-D

Thanks for your help!

Kind regards
Martin

-- 
Dipl. Wirtsch.Inf.(Univ.) Martin Eisenhardt
Otto-Friedrich-Universität Bamberg
Fakultät Wirtschaftinformatik und Angewandte Informatik
Lehrstuhl für Medieninformatik
D-96045 Bamberg
fon: +49 (951) 863-2856
fax: +49 (951) 863-2852
www: http://www.mneisen.org