This would be a good bug for somebody who has done a couple of
ProbablyEasy issues and wants something potentially more involved to tackle.

Johan Tibell made an interesting point that being able to conveniently
diff two branches is very important for a maintainer workflow.

I suggest that we introduce two flags to darcs diff (Grumpy Old Man
permitting), --from-repo and --to-repo.

The UI puzzle is to make sure that this interacts nicely with
pre-existing (or future flags).  As I understand it:
 
 * the from/to repos default to the current one
 * --index would have to be forbidden unless --from-repo == --to-repo
 * --last, --to-{tag,patch,match} would have to match within the to repo
 * --from-{tag,patch,match} would have to match within the from repo

Making Johan nosy on this ticket.

-- 
Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow>
PGP Key ID: 08AC04F9

Note that Florent has suggested issue1870 as an alternative solution to
the diff repo problem.

You could have darcs diff --repo remote --match "not in [local]"
and darcs diff --match "not in [remote]"