Comment 4 for bug 199629

The smart server over http has been an option for a long time. That page doesn't explicitly mention it (which I admit is a bit annoying), but you can enable it using the --http option to "bzr serve" if you have loggerhead installed, or you can hook it into apache - how to do so is in the documentation somewhere as well.

IIRC the main code for this is in ./bzrlib/transport/http/wsgi.py.