Hi Matwey, On Tue, 9 Jan 2018, Matwey V. Kornilov wrote:
> 2018-01-09 16:25 GMT+03:00 Johannes Schindelin <johannes.schinde...@gmx.de>: > > Hi Matwey, > > > > On Tue, 9 Jan 2018, Matwey V. Kornilov wrote: > > > >> 2018-01-08 22:36 GMT+03:00 Johannes Schindelin > >> <johannes.schinde...@gmx.de>: > >> > > >> > On Mon, 8 Jan 2018, Matwey V. Kornilov wrote: > >> > > >> >> 2018-01-08 19:32 GMT+03:00 Johannes Schindelin > >> >> <johannes.schinde...@gmx.de>: > >> >> > > >> >> > On Mon, 8 Jan 2018, Matwey V. Kornilov wrote: > >> >> > > >> >> >> 2018-01-08 17:42 GMT+03:00 Matwey V. Kornilov > >> >> >> <matwey.korni...@gmail.com>: > >> >> >> > 2018-01-08 16:56 GMT+03:00 Johannes Schindelin > >> >> >> > <johannes.schinde...@gmx.de>: > >> >> >> >> Hi Matwey, > >> >> >> >> > >> >> >> >> On Mon, 8 Jan 2018, Matwey V. Kornilov wrote: > >> >> >> >> > >> >> >> >>> I think that rebase preserve-merges algorithm needs further > >> >> >> >>> improvements. Probably, you already know it. > >> >> >> >> > >> >> >> >> Yes. preserve-merges is a fundamentally flawed design. > >> >> >> >> > >> >> >> >> Please have a look here: > >> >> >> >> > >> >> >> >> https://github.com/git/git/pull/447 > >> >> >> >> > >> >> >> >> Since we are in a feature freeze in preparation for v2.16.0, I > >> >> >> >> will > >> >> >> >> submit these patch series shortly after v2.16.0 is released. > >> >> >> >> > >> >> >> >>> As far as I understand the root cause of this that when new merge > >> >> >> >>> commit is created by rebase it is done simply by git merge > >> >> >> >>> $new_parents without taking into account any actual state of the > >> >> >> >>> initial merge commit. > >> >> >> >> > >> >> >> >> Indeed. preserve-merges does not allow commits to be reordered. > >> >> >> >> (Actually, > >> >> >> >> it *does* allow it, but then fails to handle it correctly.) We > >> >> >> >> even have > >> >> >> >> test cases that mark this as "known breakage". > >> >> >> >> > >> >> >> >> But really, I do not think it is worth trying to fix the broken > >> >> >> >> design. > >> >> >> >> Better to go with the new recreate-merges. (I am biased, of > >> >> >> >> course, > >> >> >> >> because I invented recreate-merges. But then, I also invented > >> >> >> >> preserve-merges, so ...) > >> >> >> > > >> >> >> > Well. I just checked --recreate-merges=no-rebase-cousins from the > >> >> >> > PR > >> >> >> > and found that it produces the same wrong result in my test > >> >> >> > example. > >> >> >> > The topology is reproduced correctly, but merge-commit content is > >> >> >> > broken. > >> >> >> > I did git rebase --recreate-merges=no-rebase-cousins --onto > >> >> >> > abc-0.1 v0.1 abc-0.2 > >> >> >> > >> >> >> Indeed, exactly as you still say in the documentation: "Merge > >> >> >> conflict > >> >> >> resolutions or manual amendments to merge commits are not preserved." > >> >> >> My initial point is that they have to be preserved. Probably in > >> >> >> recreate-merges, if preserve-merges is discontinued. > >> >> > > >> >> > Ah, but that is consistent with how non-merge-preserving rebase > >> >> > works: the > >> >> > `pick` commands *also* do not record merge conflict resolution... > >> >> > > >> >> > >> >> I am sorry, didn't get it. When I do non-merge-preserving rebase > >> >> --interactive there is no way to `pick' merge-commit at all. > >> > > >> > Right, but you can `pick` commits and you can get merge conflicts. And > >> > you > >> > need to resolve those merge conflicts and those merge conflict > >> > resolutions > >> > are not preserved for future interactive rebases, unless you use `rerere` > >> > (in which case it also extends to `pick`ing merge commits in > >> > merge-preserving mode). > >> > >> Are you talking about merge conflicts arising due to commits reordering? > > > > Merge conflicts can arise from commit reordering, and they can also arise > > from commits introduced in "upstream" in the meantime. > > Then I am totally agree with you. > But initially I said about conflict resolutions and amendments already > contained in existing merge-commits. While rerere can at least learn > conflict resolutions from existing merge-commits, rerere cannot learn > and recover manual amendments. Great, so the information is all there and you can implement it? :-) Ciao, Johannes
