The thing about how merges are presented seems orthogonal to how to represent history. I also hate the default in git, but that is why I just use p4merge as a merge tool and get a proper 4-pane merge tool (left, right, common base, merged result) which shows everything needed to figure out why there is a conflict and how to resolve it. I don't understand why you need to switch out the VCS to fix that issue.
<<<<<<< left
||||||| base
def calculate(x):
a = x * 2
b = a + 1
return b
=======
def calculate(x):
a = x * 2
logger.debug(f"a={a}")
b = a + 1
return b
>>>>>>> right
With this configuration, a developer reading the raw conflict markers could infer the same information provided by Manyana’s conflict markers: that the right side added the logging line.
That still have an issue with the vocabulary. Things like "theirs/our" is still out of touch but it's already better than a loose spatial analogy on some representation of the DAG.
Something like base, that is "common base", looks far more apt to my mind. In the same vein, endogenous/exogenous would be far more precise, or at least aligned with the concern at stake. Maybe "local/alien" might be a less pompous vocabulary to convey the same idea.
I'll be honest, as a fairly skilled and experienced programmer who isn't a git expert, I know what HEAD means, but when I'm rebasing I really have no idea. It all seems to work out in the end because my collaborative work is simple and usually 2–3 people only, so I'm never rebasing against a ton of commits I lack context for (because 90% of them are my commits since I'm usually dealing with PRs to my open source projects rather than someone else's).
HEAD is "the thing we're editing now" but that's not terribly useful when rebasing since you're repeatedly editing a fake history.
Git leaks a lot of implementation details into its UX. Rebasing is meant to be equivalent to checking out the "base" branch and cherry picking commits onto it. Therefore "ours" during a rebase is the base branch.
The meaning of "ours" and "theirs" is always the same, but the "base" of the operation is reversed compared to what you might be used to during merge.
Rebasing can be confusing and hard and messy, but once I learned that rule and took the time to internalize it, I at least never got confused on this particular detail again.
> fake history
That's the thing, it's not actually fake history. Git really is doing the things it looks like it's doing during a rebase. That's why you can do all kinds of weird tricks like stopping in the middle to reset back a commit in order to make a new intervening commit. The reason you can abort at any time with (almost) no risk is because the old history is still hanging around in the database and won't be removed until GC runs, usually long after the rebase is settled.
Learning git properly is pretty much "read Git book at least 3 times".
All of it makes sense and is decently intuitive once you know how internals work.
People keep imagining git as a series of diffs while in reality it's series of the filesystem tree snapshots + a bunch of tools to manage that and reconcile changes in face of merge. And most of that can be replaced if the builtins are not up to task. And the experience is getting slowly better but it's balance between power users and newbies, and also trying to not break stuff when going forward.
Now of course that sucks if programming is not someone's day job but there is plenty of tools that present simpler workflows built on top of that.
Also git store (almost?) all its operations in the reflog. They have identifier like commits so you can reset to them and restore the original state of the working directory (mostly after an automatic rebase gone wrong).
> HEAD is "the thing we're editing now" but that's not terribly useful when rebasing since you're repeatedly editing a fake history.
You got two things wrong here. Firstly, HEAD isn't 'the thing you're editing now'. HEAD is what you have already committed. If you want to edit the HEAD, you have to either amend the commit or reset and redo the commit. (To make the situation even more complex, the amended or overridden commit remains in the repo unchanged, but orphaned.)
The actual thing being edited is a 'patch' that will eventually be converted into a new commit (snapshot). If you're doing a rebase and want to see the next patch in the pipeline that you're editing now, try this:
git rebase --show-current-patch
Secondly, rebase is not editing a fake history. Rebase is creating a new (and real) history by repeatedly cherry picking commits from the old history based on the rebase plan. HEAD is the tip commit of the new history under construction. On completion of the rebase, the branch ref of the old history is switched to the new history, where HEAD is now at. Meanwhile, the old history remains in the repo unchanged, but again orphaned.
All the orphaned commits are still visible in the HEAD's reflog. You can use it to undo the rebase if you wish.
I agree that the entire thing is confusing as hell. But I have a bunch of aliases and scripts that show you the process graphically in realtime. You can use that awareness to make the right call every time. I'm thinking about converting it into a TUI application and publishing it.
This is one of my pain points, and one time I googled and got the real answer (which is why it's such a pain point).
That answer is "It depends on the context"
> The reason the "ours" and "theirs" notions get swapped around during rebase is that rebase works by doing a series of cherry-picks, into an anonymous branch (detached HEAD mode). The target branch is the anonymous branch, and the merge-from branch is your original (pre-rebase) branch: so "--ours" means the anonymous one rebase is building while "--theirs" means "our branch being rebased".[0]
>Maybe "local/alien" might be a less pompous vocabulary to convey the same idea.
That is more alien and just as contrived. If you merge branches that you made, they're both local and "ours". You just have to remember that "ours" is the branch you are on, and "theirs" is the other one. I have no idea what happens in an octopus merge but anyway, the option exists to show commit titles along with markers to help you keep it straight.
This is better but it still doesn't really help when the conflict is 1000 lines and one side changed one character and the other deleted the whole thing. That isn't theoretical - it happens quite regularly.
What you really need is the ability to diff the base and "ours" or "theirs". I've found most different UIs can't do this. VSCode can, but it's difficult to get to.
I haven't tried p4merge though - if it can do that I'm sold!
I'm on my phone right now so I'm not going to dig too hard for this, but you can also configure a "merge tool" (or something like that) so you can use Meld or Kompare to make the process easier. This has helped me in a pinch to work out some confusing merge conflicts.
> I don't understand why you need to switch out the VCS to fix that issue.
For some reason, when it comes to this subject, most people don't think about the problem as much as they think they've thought about it.
I recently listened to an episode on a well-liked and respected podcast featuring a guest there to talk about version control systems—including their own new one they were there to promote—and what factors make their industry different from other subfields of software development, and why a new approach to version control was needed. They came across as thoughtful but exasperated with the status quo and brought up issues worthy of consideration while mostly sticking to high-level claims. But after something like a half hour or 45 minutes into the episode, as they were preparing to descend from the high level and get into the nitty gritty of their new VCS, they made an offhand comment contrasting its abilities with Git's, referencing Git's approach/design wrt how it "stores diffs" between revisions of a file. I was bowled over.
For someone to be in that position and not have done even a cursory amount of research before embarking on a months (years) long project to design, implement, and then go on the talk circuit to present their VCS really highlighted that the familiar strain of NIH is still alive, even in the current era where it's become a norm for people to be downright resistant to writing a couple dozen lines of code themselves if there is no existing package to import from NPM/Cargo/PyPI/whatever that purports to solve the problem.
Seconding the use of p4merge for easy-to-use three-pane merging. Just like most other issues with Git, if your merges are painful it's probably due to terrible native UX design - not due to anything conceptually wrong with Git.
I often find myself using the gitlens in vscode, to do something similar. I'd compare the working tree to the common base. Then I have the left pane with what's already in the base, the right pane is editable with the result in it.
It's nice to have all the LSP features available too while editing.
You can't use CRDTs for version control, having conflicts is the whole point of version control. Sometimes two developers will make changes that fundamentally tries to change the code in two different ways, a merge conflict then leaves it up to the developer who is merging/rebasing to make a choice about the semantics of the program they want to keep. A CRDT would just produce garbage code, its fundamentally the wrong solution. If you want better developer UX for merge conflicts then there are both a bunch of tooling on top of Git, as well as other version control systems, that try to present it in a better way; but that has very little to do with the underlaying datastructure. The very fact that cherry-picking and reverting becomes difficult with this approach should show you that its the wrong approach! Those are really easy operations to do in Git.
Is it a good thing to have merges that never fail? Often a merge failure indicates a semantic conflict, not just "two changes in the same place". You want to be aware of and forced to manually deal with such cases.
I assume the proposed system addresses it somehow but I don't see it in my quick read of this.
The semantic problem with conflicts exists either way. You get a consistent outcome and a slightly better description of the conflict, but in a way that possibly interleaves changes, which I don't think is an improvement at all.
I am completely rebase-pilled. I believe merge commits should be avoided at all costs, every commit should be a fast forward commit, and a unit of work that can be rolled back in isolation. And also all commits should be small. Gitflow is an anti-pattern and should be avoided. Long-running branches are for patch releases, not for feature development.
I don't think this is the future of VCS.
Jujutsu (and Gerrit) solves a real git problem - multiple revisions of a change. That's one that creates pain in git when you have a chain of commits you need to rebase based on feedback.
This is sort of a revival and elaboration of some of Bram’s ideas from Codeville, an earlier effort that dates back to the early 2000s Cambrian explosion of DVCS.
Codeville also used a weave for storage and merge, a concept that originated with SCCS (and thence into Teamware and BitKeeper).
Codeville predates the introduction of CRDTs by almost a decade, and at least on the face of it the two concepts seem like a natural fit.
It was always kind of difficult to argue that weaves produced unambiguously better merge results (and more limited conflicts) than the more heuristically driven approaches of git, Mercurial, et al, because the edit histories required to produce test cases were difficult (at least for me) to reason about.
I like that Bram hasn’t let go of the problem, and is still trying out new ideas in the space.
In case the name doesn't jump out at you, this is Bram Cohen, inventory of Bittorrent. And Chia proof-of-storage (probably better descriptions available) cryptocurrency. https://en.wikipedia.org/wiki/Bram_Cohen
It's not the same as capturing it, but I would also note that there are a wide wide variety of ways to get 3-way merges / 3 way diffs from git too. One semi-recent submission (2022 discussing a 2017) discussed diff3 and has some excellent comments (https://news.ycombinator.com/item?id=31075608), including a fantastic incredibly wide ranging round up of merge tools (https://www.eseth.org/2020/mergetools.html).
This thing is really short. https://github.com/bramcohen/manyana/blob/main/manyana.py is 473 lines of dependency-free Python (that file only imports difflib, itertools and inspect) and of that ~240 lines are implementation and the rest are tests.
I think something like this needs to be born out of analysis of gradations of scales of teams using version control systems.
- What kind of problems do 1 person, 10 person, 100 person, 1k (etc) teams really run into with managing merge conflicts?
- What do teams of 1, 10, 100, 1k, etc care the most about?
- How does the modern "agent explosion" potentially affect this?
For example, my experience working in the 1-100 regime tells me that, for the most part, the kind of merge conflict being presented here is resolved by assigning subtrees of code to specific teams. For the large part, merge conflicts don't happen, because teams coordinate (in sprints) to make orthogonal changes, and long-running stale branches are discouraged.
However, if we start to mix in agents, a 100 person team could quickly jump into a 1000 person team, esp if each person is using subagents making micro commits.
It's an interesting idea definitely, but without real-world data, it kind of feels like this is just delivering a solution without a clear problem to assign it to. Like, yes merge-conflicts are a bummer, but they happen infrequently enough that it doesn't break your heart.
At this point if your VCS isn't a layer above git plumbing, nobody gonna waste time using it. Especially if the improvements are minor enough that it could be reasonably just a wrapper and still have 90% of the improvements.
> Two opaque blobs. You have to mentally reconstruct what actually happened.
Did you not discover what git diff does ? It's clearer than the presented improvement !
Plenty of 3 way merge tools supported by git too, sure, it's external tool but it's adding one tool rather than upending the workflow
> Conflicts are informative, not blocking. The merge always produces a result. Conflicts are surfaced for review when concurrent edits happen “too near” each other, but they never block the merge itself. And because the algorithm tracks what each side did rather than just showing the two outcomes, the conflict presentation is genuinely useful.
Git merge cache (git rerere) is good enough. Only problem is that it isn't shared but that could be possibly done within git format itself if someone really wanted to
I'm struggling to understand the problem this solves for me. I can see in the abstract why this might be useful, but in practice I don't see the problems.
For me, jj represents a massive step forward from git in terms of usability, usefulness, and solving problems I actually have.
I think the next step forward for version control would be something that works at a lower level, such as the AST. I'd love to see an exploration of what versioning looks like when we don't have files and directories, and a piece of software is one whole tree that can be edited at any level. Things like LightTable and Dark have tried bits of this, it would be good to see a VCS demo of that sort of thing.
Interesting idea. While conflicts can be improved, I personally don't see it as a critical challenge with VCS.
What I do think is the critical challenge (particularly with Git) is scalability.
Size of repository & rate of change of repositories are starting to push limits of git, and I think this needs revisited across the server, client & wire protocols.
What exactly, I don't know. :). But I do know that in my current role (mid-size well-known tech company) is hitting these limits today.
> the key insight is that changes should be flagged as conflicting when they touch each other
Not really. Changes should be flagged as conflicting when they conflict semantically, not when they touch the same lines. A rename of a variable shouldn't conflict with a refactor that touches the same lines, and a change that renames a function should conflict with a change that uses the function's old name in a new place. I don't think I would bother switching to a new VCS that didn't provide some kind of semantic understanding like this.
I made foo.py in ymywkkys, the base change. I added the logging line in ystzrmlq. For the other branch, I ran jj edit ym and changed the function body to just return 42 in vxuxqtnu. Finally, I generate the merge commit with jj new ym vx. The graph looks like this:
@ qttvouvl gcr@hackerne.ws 2026-03-24 10:02:56 (conflict)
├─╮ (empty) Some merge commit
│ ○ ystzrmlq gcr@hackerne.ws 2026-03-24 10:02:54
│ │ Add logging line
○ │ vxuxqtnu gcr@hackerne.ws 2026-03-24 10:02:54
├─╯ Just return 42
○ ymywkkys gcr@hackerne.ws 2026-03-24 10:02:49
│ Base function
◆ zzzzzzzz root() 00000000
In jj, merges and rebases always succeed, but they may generate conflicts which are first-class objects in the repository alongside files, changes, directories, and so on. Having a structured way of representing conflicts allows for a more structured vocabulary. For instance, "conflict markers" don't live in the file itself, they're just rendered out to the working copy whenever the working copy gets updated.
I personally find this diff harder to read than the proposed format in the post, but the same information is there:
def calculate(x):
<<<<<<< conflict 1 of 1
+++++++ vxuxqtnu "Just return 42"
return 42
%%%%%%% diff from: ymywkkys "Base function"
\\\\\\\ to: qttvouvl "Some merge commit" (rebased revision)
a = x * 2
+ logger.debug(f"a={a}")
b = a + 1
return b
>>>>>>> conflict 1 of 1 ends
380 comments
Something like base, that is "common base", looks far more apt to my mind. In the same vein, endogenous/exogenous would be far more precise, or at least aligned with the concern at stake. Maybe "local/alien" might be a less pompous vocabulary to convey the same idea.
Why not show the names of the branch + short Id (and when is not direct name, at least "this is from NAME")
HEAD is "the thing we're editing now" but that's not terribly useful when rebasing since you're repeatedly editing a fake history.
The meaning of "ours" and "theirs" is always the same, but the "base" of the operation is reversed compared to what you might be used to during merge.
Rebasing can be confusing and hard and messy, but once I learned that rule and took the time to internalize it, I at least never got confused on this particular detail again.
> fake history
That's the thing, it's not actually fake history. Git really is doing the things it looks like it's doing during a rebase. That's why you can do all kinds of weird tricks like stopping in the middle to reset back a commit in order to make a new intervening commit. The reason you can abort at any time with (almost) no risk is because the old history is still hanging around in the database and won't be removed until GC runs, usually long after the rebase is settled.
All of it makes sense and is decently intuitive once you know how internals work.
People keep imagining git as a series of diffs while in reality it's series of the filesystem tree snapshots + a bunch of tools to manage that and reconcile changes in face of merge. And most of that can be replaced if the builtins are not up to task. And the experience is getting slowly better but it's balance between power users and newbies, and also trying to not break stuff when going forward.
Now of course that sucks if programming is not someone's day job but there is plenty of tools that present simpler workflows built on top of that.
> HEAD is "the thing we're editing now" but that's not terribly useful when rebasing since you're repeatedly editing a fake history.
You got two things wrong here. Firstly, HEAD isn't 'the thing you're editing now'. HEAD is what you have already committed. If you want to edit the HEAD, you have to either amend the commit or reset and redo the commit. (To make the situation even more complex, the amended or overridden commit remains in the repo unchanged, but orphaned.)
The actual thing being edited is a 'patch' that will eventually be converted into a new commit (snapshot). If you're doing a rebase and want to see the next patch in the pipeline that you're editing now, try this:
Secondly, rebase is not editing a fake history. Rebase is creating a new (and real) history by repeatedly cherry picking commits from the old history based on the rebase plan. HEAD is the tip commit of the new history under construction. On completion of the rebase, the branch ref of the old history is switched to the new history, where HEAD is now at. Meanwhile, the old history remains in the repo unchanged, but again orphaned.All the orphaned commits are still visible in the HEAD's reflog. You can use it to undo the rebase if you wish.
I agree that the entire thing is confusing as hell. But I have a bunch of aliases and scripts that show you the process graphically in realtime. You can use that awareness to make the right call every time. I'm thinking about converting it into a TUI application and publishing it.
That answer is "It depends on the context"
> The reason the "ours" and "theirs" notions get swapped around during rebase is that rebase works by doing a series of cherry-picks, into an anonymous branch (detached HEAD mode). The target branch is the anonymous branch, and the merge-from branch is your original (pre-rebase) branch: so "--ours" means the anonymous one rebase is building while "--theirs" means "our branch being rebased".[0]
[0] https://stackoverflow.com/questions/25576415/what-is-the-pre...
>Maybe "local/alien" might be a less pompous vocabulary to convey the same idea.
That is more alien and just as contrived. If you merge branches that you made, they're both local and "ours". You just have to remember that "ours" is the branch you are on, and "theirs" is the other one. I have no idea what happens in an octopus merge but anyway, the option exists to show commit titles along with markers to help you keep it straight.
What you really need is the ability to diff the base and "ours" or "theirs". I've found most different UIs can't do this. VSCode can, but it's difficult to get to.
I haven't tried p4merge though - if it can do that I'm sold!
> I don't understand why you need to switch out the VCS to fix that issue.
For some reason, when it comes to this subject, most people don't think about the problem as much as they think they've thought about it.
I recently listened to an episode on a well-liked and respected podcast featuring a guest there to talk about version control systems—including their own new one they were there to promote—and what factors make their industry different from other subfields of software development, and why a new approach to version control was needed. They came across as thoughtful but exasperated with the status quo and brought up issues worthy of consideration while mostly sticking to high-level claims. But after something like a half hour or 45 minutes into the episode, as they were preparing to descend from the high level and get into the nitty gritty of their new VCS, they made an offhand comment contrasting its abilities with Git's, referencing Git's approach/design wrt how it "stores diffs" between revisions of a file. I was bowled over.
For someone to be in that position and not have done even a cursory amount of research before embarking on a months (years) long project to design, implement, and then go on the talk circuit to present their VCS really highlighted that the familiar strain of NIH is still alive, even in the current era where it's become a norm for people to be downright resistant to writing a couple dozen lines of code themselves if there is no existing package to import from NPM/Cargo/PyPI/whatever that purports to solve the problem.
Perhaps the value of doing it on SCM level is that it can remember what you did. Git has some not-so-nice edge cases.
It's nice to have all the LSP features available too while editing.
I assume the proposed system addresses it somehow but I don't see it in my quick read of this.
The semantic problem with conflicts exists either way. You get a consistent outcome and a slightly better description of the conflict, but in a way that possibly interleaves changes, which I don't think is an improvement at all.
I am completely rebase-pilled. I believe merge commits should be avoided at all costs, every commit should be a fast forward commit, and a unit of work that can be rolled back in isolation. And also all commits should be small. Gitflow is an anti-pattern and should be avoided. Long-running branches are for patch releases, not for feature development.
I don't think this is the future of VCS.
Jujutsu (and Gerrit) solves a real git problem - multiple revisions of a change. That's one that creates pain in git when you have a chain of commits you need to rebase based on feedback.
Codeville also used a weave for storage and merge, a concept that originated with SCCS (and thence into Teamware and BitKeeper).
Codeville predates the introduction of CRDTs by almost a decade, and at least on the face of it the two concepts seem like a natural fit.
It was always kind of difficult to argue that weaves produced unambiguously better merge results (and more limited conflicts) than the more heuristically driven approaches of git, Mercurial, et al, because the edit histories required to produce test cases were difficult (at least for me) to reason about.
I like that Bram hasn’t let go of the problem, and is still trying out new ideas in the space.
It's not the same as capturing it, but I would also note that there are a wide wide variety of ways to get 3-way merges / 3 way diffs from git too. One semi-recent submission (2022 discussing a 2017) discussed diff3 and has some excellent comments (https://news.ycombinator.com/item?id=31075608), including a fantastic incredibly wide ranging round up of merge tools (https://www.eseth.org/2020/mergetools.html).
However/alas git 2.35's (2022) fabulous zdiff3 doesn't seems to have any big discussions. Other links welcome but perhaps https://neg4n.dev/blog/understanding-zealous-diff3-style-git...? It works excellently for me; enthusiastically recommended!
> ... CRDTs for version control, which is long overdue but hasn’t happened yet
Pijul happened and it has hundreds - perhaps thousands - of hours of real expert developer's toil put in it.
Not that Bram is not one of those, but the post reads like you all know what.
- What kind of problems do 1 person, 10 person, 100 person, 1k (etc) teams really run into with managing merge conflicts?
- What do teams of 1, 10, 100, 1k, etc care the most about?
- How does the modern "agent explosion" potentially affect this?
For example, my experience working in the 1-100 regime tells me that, for the most part, the kind of merge conflict being presented here is resolved by assigning subtrees of code to specific teams. For the large part, merge conflicts don't happen, because teams coordinate (in sprints) to make orthogonal changes, and long-running stale branches are discouraged.
However, if we start to mix in agents, a 100 person team could quickly jump into a 1000 person team, esp if each person is using subagents making micro commits.
It's an interesting idea definitely, but without real-world data, it kind of feels like this is just delivering a solution without a clear problem to assign it to. Like, yes merge-conflicts are a bummer, but they happen infrequently enough that it doesn't break your heart.
> Two opaque blobs. You have to mentally reconstruct what actually happened.
Did you not discover what git diff does ? It's clearer than the presented improvement !
Plenty of 3 way merge tools supported by git too, sure, it's external tool but it's adding one tool rather than upending the workflow
> Conflicts are informative, not blocking. The merge always produces a result. Conflicts are surfaced for review when concurrent edits happen “too near” each other, but they never block the merge itself. And because the algorithm tracks what each side did rather than just showing the two outcomes, the conflict presentation is genuinely useful.
Git merge cache (git rerere) is good enough. Only problem is that it isn't shared but that could be possibly done within git format itself if someone really wanted to
For me, jj represents a massive step forward from git in terms of usability, usefulness, and solving problems I actually have.
I think the next step forward for version control would be something that works at a lower level, such as the AST. I'd love to see an exploration of what versioning looks like when we don't have files and directories, and a piece of software is one whole tree that can be edited at any level. Things like LightTable and Dark have tried bits of this, it would be good to see a VCS demo of that sort of thing.
Of significance here because the resolution strategy from merges was deeply at the disagreement between Bram and Linus.
https://web.archive.org/web/20110728005409/http://www.wincen...
What I do think is the critical challenge (particularly with Git) is scalability.
Size of repository & rate of change of repositories are starting to push limits of git, and I think this needs revisited across the server, client & wire protocols.
What exactly, I don't know. :). But I do know that in my current role (mid-size well-known tech company) is hitting these limits today.
> the key insight is that changes should be flagged as conflicting when they touch each other
Not really. Changes should be flagged as conflicting when they conflict semantically, not when they touch the same lines. A rename of a variable shouldn't conflict with a refactor that touches the same lines, and a change that renames a function should conflict with a change that uses the function's old name in a new place. I don't think I would bother switching to a new VCS that didn't provide some kind of semantic understanding like this.
I made
In jj, merges and rebases always succeed, but they may generate conflicts which are first-class objects in the repository alongside files, changes, directories, and so on. Having a structured way of representing conflicts allows for a more structured vocabulary. For instance, "conflict markers" don't live in the file itself, they're just rendered out to the working copy whenever the working copy gets updated.foo.pyin ymywkkys, the base change. I added the logging line in ystzrmlq. For the other branch, I ranjj edit ymand changed the function body to justreturn 42in vxuxqtnu. Finally, I generate the merge commit withjj new ym vx. The graph looks like this:I personally find this diff harder to read than the proposed format in the post, but the same information is there: