[darcs-users] Interesting article about how Darcs does the merge better than the most other DVCS

[Michael Olney]

Let's suppose that Darcs does produce the same result no matter what
order patches are merged in. That would not necessarily imply that it
is more or less consistent than Git. For a start, the term
"consistent" has to be defined. The arrows in Git's history DAG aren't
patches, so the manner in which such a notion would defined for both
systems is not clear to me.

Git is a snapshotting system that simply merges a set of
representative changes between a base snapshot and two derived
snapshots. The history DAG is, so far as I can tell, just an
abbreviated command history that gives hints to the merging process.
If you bare that in mind none of this is "inconsistent".

Cases like the one cited in the article are a problem (and are well
worth pointing out) because if they occur, the user probably didn't
mean them to. In any given system, we'd probably like to warn users of
any such hint that they might be making a mistake. However, the
presence or absence of these cases alone doesn't seem to tell us much
of significance about the relative merits of different systems.

On 30 April 2011 16:39, Ganesh Sittampalam <ganesh at earth.li> wrote:
> Darcs always produces the same merge result, whatever order you do
> merges in. There's no formal proof of this from the ground up, unless
> there's one for Camp yet, but our test suite does contain randomised
> tests of this property for 3 patches, and there is a semi-formal proof
> kicking around that if this property is true for 3 patches, it's true
> for any number of patches.
>
> Known exceptions are the "setpref" patches which are buggy, and also by
> design if there's a conflict the marks you get in your working copy
> aren't consistent - but the "pristine" repository should be consistent.
>
> On 30/04/2011 07:15, Michael Olney wrote:
>> The article points out a  case where Git can produce multiple results
>> (which IMO would ideally trigger a manual resolution), but does not
>> demonstrate that Darcs does any better in general. Perhaps Darcs does
>> produce more "consistent" patches than Git does. As far as I know that
>> is yet to be satisfactorily stated let alone demonstrated to be true.
>>
>> On 17 April 2011 21:09, Sven Strittmatter <weltraumschaf at googlemail.com> wrote:
>>> Hi *,
>>>
>>> http://r6.ca/blog/20110416T204742Z.html
>>>
>>> -Sven
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