RFC: bzr --version should also announce installed plugins

[John Arbash Meinel]

Jari Aalto wrote:
> Consider this Cygwin example:
>  
>     $ bzr --version
> 

We have 'bzr plugins' to list installed plugins. (We've already loaded
them, so it isn't hard to generate the list).

And it isn't quite as simple as just looking at bzrlib/plugins, because
we search all of BZR_PLUGIN_PATH.

My first instinct is to not put that info in 'bzr --version'. But it
could be interesting to have plugins support a version request (def
plugin_version()?)

Right now plugins can provide 'test_suite()' and 'bench_suite()', and we
will use it when running 'selftest'.

So it seems possible to have plugins provide something like
'plugin_version()', and have that included in 'bzr --version'.


Anyway, right now there aren't any plugins which would report what
version they are. So this requires changes to both the internals, and to
all plugins that would want to be included.

John
=:->