[RFC] Automatic Plugin Suggestion

[Martin Pool]

I'd like to see a clear separation into two interfaces, providers for
which can be registered separately (or together):

1- A lookup provider tells you what plugin offers a given topic,
command, format, etc, and outputs the plugin name (and possibly a dict
of other info, like a version)
2- An install provider that takes a plugin name, and either installs
it, or tells you how to.

We can provide default implementations of both in bzrlib which:

- look up plugins by consulting a static table in the source tree,
which we can update through the usual BB/pqm mechanism
- just prints a message asking people to install the plugin from the
bzr web page

Then they can evolve in different directions.  We can try, if desired,
doing lookups from the net, or by consulting a list of plugins
packaged for a particular system.  Or you can take the default plugin
suggestion and install it by apt or some other mechanism.

I just skimmed your patch and haven't read it properly yet.  Can I ask
that you please take the spec from the wiki and include it in the
patch, so that we have something in the developer documentation
explaining how this works, and how it will work in future.

-- 
Martin