w-changeset: merge errors out

[Aaron Bentley]

Erik Bågfors wrote:
> I say that this almost takes us all the way to
> http://bazaar-vcs.org/SubmitByMail
> But not quite.
> 
> By adding the last few pieces, it can replace pqm....

Email submission is definitely a good application for them.  I think 
they could also be useful for undo/redo, and it would be nice if 
uncommit created a changeset, too.

I'd like to focus on getting changesets merged into the core, and then 
we can work on all these things, in the core or as plugins, as appropriate.

Aaron