Expose bzr source code?

Personally, I'd configure my web server (apache) to redirect like this:

RedirectMatch temp ^/trac-env/browser/(.*/\.bzr/.*)$ /bzr-repo/$1

Or, if you don't like the extra /bzr-repo tree in your URLs, you can use mod_rewrite to rewrite to a file system path:

RewriteEngine on
RewriteRule ^/trac-env/browser/(.*/\.bzr/.*)$ /srv/bzr-repo/$1

Both of these approaches lack the access control which trac can provide, though. On the other hand, combining that access control with the bzr command line tool might be tricky. I'll welcome patches addressing this in trac, or extending the documentation to suggest methods like those outlined above.

It would be nice to expose the smart server over http, which should result in significantly better performance (and less roundtrips) than access over plain HTTP.

http://doc.bazaar.canonical.com/beta/en/user-guide/server.html sounds like a smart server over http still isn't an option. Has this changed? If so, where do I find instructions about setting up a smart server for operation over http? Or in other words, where in bzrlib are the entry points to run such a server?

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.