problem: deleting .svn directories with geant

Dear all:

I am trying to get geant to delete all .svn directories in a project.
>From the root Gobo build.eant script I found the excerpt:

<delete>
  <directoryset directory="." include="@(**/.svn)"/>
</delete>

When I run it I get:

----
F:\src\erl_g>geant delivery
  [delete] error: cannot delete directory '.svn'
----

I couldn't find any documentation on the directoryset element, so maybe
somebody here knows what the correct script would look like.

many thanks in advance,
Andreas