[RFC] Multi-parent diffs

[Martin Pool]

> I've drafted a spec for a new diff representation that I think we should
> consider adopting:
>
> http://bazaar-vcs.org/DraftSpecs/MultiparentDiffs

I can see how diffing against all parents would produce a smaller diff
in some cases, particularly when we're diffing the annotations too.

However, to extract a text stored this way would require first
building all of the parents, and that might be substantially more
work.  So maybe it would be interesting to prototype enough of this to
assess what effect it has on size and speed.

-- 
Martin