Re: [tlug] Open-source repository question

["Stephen J. Turnbull" <stephen@example.com>]

John Fremlin writes:
 > For a slightly contrived way of making the original darcs blow up, you 
 > could have:

Sure, but this "contrived sequence of patches" also "blows up" the
current heuristic that identical hunks don't conflict.

 > It's not relevant to the theory at all, it's just a decision of the 
 > conflict black box.

If you need an oracle for conflicts, you don't really have a patch
theory at all.  In fact the published theory (such as it is) does have
criteria for conflict in it, and the theorems about commutation are
specific to those criteria.  You cannot put just any "black box" into
the "patch theory" appendix or into "camp" (AIUI) and derive a new VCS
as a corollary.

 > > No, it's not.  Darcs is designed to be smarter about what is and isn't
 > > a conflict, but if it detects a conflict, Darcs throws the whole thing
 > > into the user's lap just like all the others.  And in fact I don't
 > > think Darcs really does much better than the heuristics build into git
 > > (like "patches which don't touch the same file don't conflict").
 > 
 > It doesn't do better we I think we agree. You call it being "smarter" I 
 > call it "worrying" but it seems to amount to the same thing ;-)

Well, not really.  Both git and Darcs do "worry" about conflicts.  For
example, git could simply check whether your branch is an ancestor of
the one you're pulling from (or a descendent of the branch you're
pushing to), and otherwise do nothing.  *That* would be refusing to
worry, and it would still be a useful tool for communicating patch
content (though much less useful than git).

But in fact git only does that in certain circumstances.  Normally it
will try to merge, which requires detecting conflicts, and marking
them if they're found.  Darcs just tries harder to avoid conflicts.

 > You claim that git is Turing complete?

No, I said it was a specialization....