From the changelog of the trunk package (unreleased 0.6.22):
[ Eddy Petrișor ]
* IMPORTANT: changed default behaviour of saving the configuration in
.svn/deb-layout by default to avoid stale data to override the
configuration options that were updated in the repository.
As a consequence, a new option --svn-savecfg was added to allow a
mechanism for easily overriding options locally
BTW, did you know that svn-buildpackage is maintained in collab-maint and welcomes contributions and committers/reviewers (especially those)?
In case you want to help, this is the place to start from:
svn co svn+ssh://svn.debian.org/svn/collab-maint/deb-maint/svn-buildpackage/trunk
svn co svn://svn.debian.org/svn/collab-maint/deb-maint/svn-buildpackage/trunk
If you don't have commit access to collab-maint yet (just make a request on the alioth tracker and that will be fixed ;-) ).