Bazaar commands

While in Argentina, I got around to doing something that I've wanted to do for ages: refactor Bazaar's "serve" command. It's been bugging me for a while, since we actually duplicate some of that code in Launchpad, and we keep getting bitten by changes to cmd_serve. There's also another, deeper reason why I wanted to do it.

Bazaar isn't just a version control system, it's also a very good version control library. It's very easy to figure out, use and test. I'm almost tempted to say "beautiful". In any case, if you're writing a Python library, you should probably copy bzrlib.

Except for bzrlib/builtins.py, which is where all of the built-in commands like "serve" live. For one reason or another, it's full of massive run() methods. Many of these methods contain logic that plugin authors end up copying and pasting — blech. Hence, refactoring cmd_serve.

If you are keen to learn how a version control system works, you could do a lot worse than dive into bzrlib/builtins.py, figure out what a particular command is doing, then refactor that command so the code speaks for itself. There are 64 commands in core Bazaar: get cracking!