Comment 3 for bug 412930

See the associated branch for a patch that allows:

Overriding the default user plugin directory:
``BZR_PLUGIN_PATH='/path/to/my/other/plugins'``

Disabling the site directory while retaining the user directory:
``BZR_PLUGIN_PATH='-site:+user'``

Disabling all plugins (better achieved with --no-plugins):
``BZR_PLUGIN_PATH='-user:-core:-site'``

Overriding the default site plugin directory:
``BZR_PLUGIN_PATH='/path/to/my/site/plugins:-site':+user``