[darcs-users] An example of a "complicated" change?

[Daniel Carrera]

Guillaume Hoffmann wrote:
>> Can anyone give me an example of one such merge that is "complicated" in a
>> different VCS (e.g. requires several steps, or human intervention) but is
>> simple in Darcs?
> 
> Simple: you have 3 repos A, B and C, A being the "central", B and C
> being "sons" of A.
> 
> Assume B and C have a list of independent changes made above a common
> history present in A. Then, when you want to propagage these histories
> between B and C, you have to create "merge patches" that explicitely
> do the operation. This happens in Git, Mercurial and Bazaar, with Git
> having the advantage of creating the merge patch automatically. So Git
> comes closest to darcs on this task (no extra human intervention).

Something I don't understand. Why does your example require 3 
repositories? Why doesn't this work with 2 repositories? Like this:

Alice has a repository with patch A. Bob pulls the patch and adds patch 
B. Then Alice adds patch C to her own repository.

Why would this case be any different than the 3-repository case?

Daniel.