[Haskell-cafe] Re: Darcs - dependencies between repositories (aka forests)

[Ganesh Sittampalam]

On Sun, 29 Mar 2009, Peter Verswyvelen wrote:

> Module A requires B. When a new developer wants to get the source code, he
> does a "darcs get server://program/A", which gives him only the latest
> version of A. So he manually needs to do "darcs get server://program/B"
> (that B is required is usually discovered after a compilation error, talking
> to other developers to find out what the dependencies are, or by reading the
> cabal file). Furthermore it is unclear which version of A required which
> version of B (so you can't really roll back to old versions).
>
> Now assume you don't have 2 modules but dozens...
>
> To me, any version control system should be able to track dependencies
> between repositories. Something similar like Cabal's dependency system.
>
> So my question is really, how do you solve the dependency tracking between
> several Darcs repositories?

There's an (unimplemented) proposal by David Roundy for darcs sub-repos 
that would solve this problem: you have a darcs patch type 
that means "depend on this patch from this other darcs repo which will be 
checked out in a given subdirectory". I think that solves precisely the 
problem you describe, and I think it should be implemented :-)

Ganesh