I don't know if this is a genuinely useful thing to have, or if it should just
be something for the library.

But maybe it would be good to have a darcs show deps command, which outputs a
graph representing patch dependencies (minimal context!) for a given set of
patches, defined by matchers.  The graph could be written in some "standard"
language like Graphviz's dot notation, as suggested by Trent.

I'm adding Ian because of his camp-view tool.

I think this would be really nice.

Here is a use case:

1) Alice writes 'A' to 'file'.
2) Bob gets the repo.
3) Alice changes 'A' to 'B'.
4) Bob changes 'A' to 'C'
5) Bob pulls and resolves the 'B vs C' conflict by writing 'D'.

Now Bob has 4 patches, like:

  B---D
 /   /
A---C

So A depends on nothing, B depends on A, C depends on A, D depends on B and C.

In case darcs show deps could show this info, that would be really nice.

This is a duplicate of issue927.  I've added all nosy users to that bug.