Figuring out a workflow (bzr-svn, local changes I never want to push upstream)

[Tom Tobin]

At work, I just switched from using svn to bzr-svn to work against our
Subversion repository.  (I already happily use Bazaar for everything
else.)  I'm having a bit of trouble figuring out a sane workflow,
though.  There are a few changes I've made locally to match my
environment (vs. our production environment), and I don't ever want to
push those upstream; so far, I've been doing the following awkward
dance (everything's in a shared repository):

cd shared_repo/trunk (this is the bzr-svn branch)
bzr pull
cd ../local (this is a branch off of trunk with an extra commit for
the aforementioned local changes)
bzr rebase
cd ../feature_branch (this is a branch off of local)
bzr rebase
[hack hack hack]
bzr ci -m "hack hack hack"
cd ../trunk
bzr merge -r -2..-1 ../feature_branch
bzr dpush
cd ../local
bzr rebase
cd ../feature_branch
bzr rebase (now I get spurious history, with both the upstream svn
commit and the bzr commit for "hack hack hack", as well as the
local-change commit showing up twice)

I *have* to be doing something utterly wrong/insane; can anyone point
it out to me?  :-)