import tariffs

[Martin Pool]

One way we can speed up Bazaar is to load less code at startup: this
particularly helps on machines with magnetic disks and cold caches,
but it's a good idea everywhere.  There are various things we can do
including making things lazily loaded from registries and trimming
unnecessary imports.  People have patched these in the past but it is
easy for them to regress.

<https://code.edge.launchpad.net/~mbp/bzr/tariff/+merge/18970> adds a
framework for checking what is loaded and some documentation;
<https://code.edge.launchpad.net/~mbp/bzr/trim-imports/+merge/18971>
is a small example of using it.

The next big step is probably to make more commands be lazily loaded.

-- 
Martin <http://launchpad.net/~mbp/>