breaking change: repository structure, deploy interface

[Clint Byrum]

Excerpts from William Reade's message of Wed Sep 28 19:10:31 -0700 2011:
> Hi all
> 
> The good news is that I'm just about to merge a branch which brings us a
> significant step closer to using remote charm repositories.
> 

W00t!

> The bad news is that is requires you to make two changes which are not
> compatible with Juju's current implementation, as follows:
> 
> 
> * Repository structure
> 
> Local repositories are no longer flat: they require subdivision by
> Ubuntu series codename. In practice, you should be able to:
> 
> (1) create a directory called "oneiric" in your current repository, and
> move all your charms inside
> (2) if you're not running oneiric locally, add "default-series: oneiric"
> to your environment config file
> 

This default selection based on the local machine series seems
totally arbitrary.  While we hope the world runs Ubuntu, the reality
is that many of our users will be using juju from OS X, or maybe even
Fedora/CentOS/RHEL... FreeBSD maybe?

I think we can safely set the default series to just 'oneiric' and when
the next series is "released" in the charm repository, bump the default
in juju to that, noting the update. Making this so dynamic will, I think,
harm repeatability of deployments.

> I hope this is all clear, and not too desperately inconvenient. We don't
> expect this work to break anything else after this.

Its quite clear and all makes sense. Thanks for the heads up!