On Wed, Oct 10, 2007 at 08:48:31AM -0700, David Brown <git@xxxxxxxxxx> wrote: > On Wed, Oct 10, 2007 at 08:25:15AM -0700, Linus Torvalds wrote: > >Yes, *some* SCM's have tried to do that. In particular, the ones that are "patch-based" tend to think that patches are "identical" regardless of where they are, and while re-ordering of them is a special event, it's not somethign that changes the fundamental 'ID' of the patch. > >For example, I think the darcs "patch algebra" works that way. > >It's a really horrible model. Not only doesn't it scale, but it leads to various very strange linkages between patches, and it fails the most important part: it means that merges get different results just because people are doing the same changes two different ways. > Actually, specifically darcs, different merges _always_ result in the same > data. It's a fundamental part of is patch algebra. No matter what order > you apply a given set of patches, even with conflicts and reordering, you > always get the same result, or no result. Conflicts are "resolved" by > inserting conflict markers in the file, ordered by the patch ID. It > doesn't matter which order you apply them in, you get the same markers. > Then there will be a merge patch which fixes the markers that someone could > apply, no matter what order the applied the previous patches. > Darcs breaks down in a few places, though. > - The no result. Sometimes, it just can't figure out how to reorder > patches. Even worse, occasionally, the implementation will fail to > terminate try to figure this out. There isn't much to do at this > point, except manually apply the patch, hence generating a new patch > ID. > - It doesn't scale well. > The strange linkages between patches could be thought of as a feature, > since it is basically constraining the order that the patches can be > applied in. > There is a darcs-git project that tries to do the darcs things on top of > git. > Dave > - > To unsubscribe from this list: send the line "unsubscribe git" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html thanks, - VMiklos
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