Anyway, I'm thinking about the following approach:
1. Add a "dist" target to the Makefile of the source package.
2. Build the tarball from SVN by doing make dist.
Perhaps a time stamp in dist.stamp or something makes
sense.
3. In this proces debian/control (which should be _not_ checked
in into SVN, because it is auto generated) should be builded.
It should _not_ be touched later on.
4. Perhaps we add a line:
XS-Warning: Do not touch this control file manually. It is
auto generated blabla
(Please correct me if I'm wrong, but XS-* tags should be
ignred and thus we could use it as comment, right?
This should solve on the one hand the problem of generating an
up to date debian/control (in case we let not rot the source tarball
very long anywhere) while beeing able to get rid of this
network at bauild time / download stuff which belongs to source
etc stuff.