Hacker News new | ask | show | jobs
by marcuskaz 297 days ago
> Jujutsu is more powerful than Git. Despite the fact that it's easier to learn and more intuitive, it actually has loads of awesome capabilities for power users that completely leave Git in the dust.

Like? This isn't explained, I'm curious on why I would want to use it, but this is just an empty platitude, doesn't really give me a reason to try.

7 comments

Hi, author here. Since the target audience is people with little to no Git experience, a detailed comparison would not make sense. I did simply make that claim because the weirdness of Git's UI is usually justified by saying how powerful it is. So this statement is just intended to ease the readers mind that they're not missing out on power by choosing a tool that's easier to learn.
I appreciate this perspective.

IMO, the authors and evangelists of Git are essentially correct when they argue about its power.

However, I think that it's extremely difficult to gain practical experience with using Git in a high-powered, high-agency way, mostly because there are a lot of abstract concepts at play and there is no easily accessible place where these concepts can be "discovered".

Basically, Git is as good as it's cracked up to be, but only if you're an expert.

If you're interested in becoming a Git expert, I cannot recommend Emacs Magit strongly enough.

If not, I think Jujutsu could be an quicker road to a high-agency version control workflow. It's at least worth considering. I feel confident that Jujutsu can succeed, in particular because of Git's harsh difficulty curve.

Thanks, but I consider myself a Git expert already :-) I read the Pro Git book cover to cover. I have a gluten-free, artisanal, free-range git config that I've grown and cared for over years. single character aliases all the important commands, "log all graph oneline", "commit amend no-edit", interactive rebase (ofc. with autosquash, autostash, updaterefs and rebasemerges), reset hard, push force-with-lease... Also: commit signing, url rewriting, conditional configs for different orgs, all that jazz. I was super productive with it and loved it.

And then Jujutsu came along and casually doubled my VCS productivity. I didn't see it coming!

Is there a particular pain point (or set of pain points) that you have using git which is removed when you use Jujutsu?

I am interested to know, because there seem to be a small number of people who really seem to like it, and up to this point I haven't been able to understand what it is that they are all so excited about.

For me, it's two things:

1. I understood git better after ten minutes of jj than after fifteen years of git. Git just doesn't expose its underlying data model as well as jj does. I guess, if you already know git well, this isn't going to make a difference for you.

2. This question is a bit like asking what can I do with a calculator that I can't do with pen and paper? Technically, nothing, but everything will be so much easier that you'll be much more likely to use it. Even though I can, technically, stash my worktree and jump to another commit with git, it's so fiddly to unstash (especially with multiple stacked switches/stashes) that I just never did it.

With jj, I leave commits in the middle and jump to other commits (to fix a bug or make a small change I noticed I need while working on a larger change) all the time, because there's zero friction.

jj just removes all the friction that's prevalent in git. Things are easy in jj that in git are merely possible.

> With jj, I leave commits in the middle and jump to other commits (to fix a bug or make a small change I noticed I need while working on a larger change) all the time, because there's zero friction.

For git users who are wondering "What friction? I just git stash and jump to another branch":

In jj, you just jump without needing to type any command like git stash.

I've taken to summing it up as "jj makes everyone the git guru".
I would think the obvious answer is how jj deals with merge conflicts.

In git, if you get a conflict, you feel like you have to resolve it now.

With jj, most of the times I get merge conflicts, I simply ignore them and deal with them later. A conflict is not at all a blocker.

> In git, if you get a conflict, you feel like you have to resolve it now.

I guess I view that as a positive rather than a negative. I'm not saying that dealing with merge conflicts is a picnic -- it isn't. I just find it difficult to believe that ignoring them and resolving them later will improve the situation in the long run.

> With jj, most of the times I get merge conflicts, I simply ignore them and deal with them later.

Sorry? You what? How do you know which bit from which source goes where?

Yes and no.

Before I started using Jujutsu, I didn't have any pain points with using Git. I didn't understand what all the fuss was about. Git works well! So I totally understand how most Git users have that same reaction when hearing about Jujutsu.

I think the reason I even tried it out in the first place was because Steve Klabnik wrote a tutorial about it. I have a lot of respect for him, because the Rust book is really good. So I though: If Steve thinks it's worth it, I should probably check it out.

Now that I'm used to jj, going back reveals like 100 things that are immediately super annoying when using git. I don't feel like writing it all down TBH. :-) In a general sense, Jujutsu get's out of your way much better than Git. There are a lot of situations where Git blocks you from continuing to work. Have a merge conflict? Stop working, fix it right now. Want to check out another branch? Nu-uh, clean up your dirty worktree first. jj doesn't do that. Have a conflict? I'll record it in the commit, fix it whenever you like. Checking out another branch? No worries, I'll keep your work in progress safe in a commit.

for me, everything git is a pain point. But its not so much painpoints that it addresses, as it is that it just makes entirely new things dead-simple to do, especially via jjui.

"megamerges" are one such example. ive shared many links, here and in other posts

> for me, everything git is a pain point

Yeah, I was looking for something (or "things") specific. An "I hate everything about it" explanation doesn't really compel me to try out the alternative.

> "megamerges" are one such example. ive shared many links, here and in other posts

I read through one megamerge link you shared ( https://v5.chriskrycho.com/journal/jujutsu-megamerges-and-jj... ). So the argument seems to be (forgive me if I'm reading this wrong), if you have multiple versions of a single set of source files that all have differing changes, for you JuJutsu makes it easier (easier then git, that is) to merge them into the final commit you want to end up with. Is that correct?

Just trying to make sure I understand. Honestly, after reading that article I am still not feeling the need to try Jujustu out. I'm still open to being convinced, but have yet to see anything that makes me go "wow, I need to try that!".

> If you're interested in becoming a Git expert, I cannot recommend Emacs Magit strongly enough.

Yes, Emacs' Magit and Git Cola.

vim-fugitive
I suppose I want the article written for the experienced developer, convince me why I should try something different than the huge defacto standard that is git. I'm totally open to trying something new, but need a compelling case.

Beyond `jj undo` everything else in this thread feels just as complicated as git.

A couple of them seem more complicated, like the example further up on the page for postponing merge conflicts. In git I'd just abort the merge and do it later.

I also found the exchange about named branches funny, that ends with:

> Ok, you need to call `jj bookmark set -r@ XYX` (or `jj b s -r@ XYX`), so what?

Apparently this is excusable, but people like to complain about git's commands being too obtuse - as far as I understand the git version is "git checkout -b XYX", right? (Or I guess "git switch -c XYX" with the new commands)

> as far as I understand the git version is "git checkout -b XYX"

The difference is actually worse than that. There is not the regular git equivalent, because this step is just done implicitly for you, normally. That is, with jj, just because you had checked out the head of main and then you added a new commit, doesn't mean your new commit is now the new head of main. `jj bookmark set -r@ main` is the way you tell jj to actually advance main to your latest commit.

But you are right - `git switch -C main` would be more or less the equivalent in git if you were working in detached head mode, which is how jj normally works (note the `-C`, not `-c`, to forcefully update main to point to this commit).

That’s backwards, your git command is “move to this branch” and the jj command is “update where the branch points to,” so git reset —hard.
The git commands are "create new branch at HEAD and switch to it", and the context of the thread above sounded like that's the functionality they wanted?
“jj bookmark set” doesn’t create a new branch and switch to it. It updates the head of an existing branch to a new place.

jj doesn’t have a “name a new branch and switch to it” command, because you usually don’t bother naming branches until you’re using them up to a forge, and there’s no “current branch” concept. I creat new named branches with “jj git push -c” which names it for me, and switching branches is closest to jj new or jj edit.

They're closer to the right command than you are. `git reset --hard` will move HEAD to the given branch. The right command would be `git checkout -B branch` / `git switch -C branch`, to create or update `branch` to point to the current commit (except for the side effect that future commits will then go onto `branch` in git, while they won't in jj).

Basically, jj is just like working with git in detached head mode as far as I can tell.

You know, I was in the middle of some long flights and missed the -b! You’re right about that part, that’s my bad! I’m starting to forget git details at this point, haha. (I never used switch, always checkout -b)
do you know about git rerere? if yes, you might like jj.
This made me laugh. Thank you.
It’s funny because it’s true! ;)
There isn't a single thing in jj that's as complicated as git. I could go on to list a few features, but it would sound underwhelming, because you could do all that in git.

It's kind of like asking "why would I buy a digital camera when my film camera does all the same things? I can already see what the photo will look like when I take it, and developing my own film isn't that much of a hassle", yet film cameras have gone the way of the dodo, except for the occasional nostalgic enthusiast.

I don't think this is what the person you responded to is asking.

Their question is more, "why would I buy a digital camera that takes pictures in a new format that only a few cameras understand? All my tooling, 3rd parties, and other camera I own use the standard format. Even though I can see why the new format has advantages, I am still going to have to use the other format for all these other photos I have to work with, and there aren't equivalent tools in the new format for all these other photos things I need to do. Even if I buy this new camera, I am still going to have to work with the old format, so I'll have to learn how to use two formats now, and get used to two tool chains. Since the existing format is something I am going to have to use either way, how is it worth it for me to have to use two formats?"

You don't have two formats, though. Jj transparently works with git. I use it for everything and none of my collaborators is even aware that I'm using jj.
If you say that you can work only with JJ and never use git, you are delusional. For one, where is that JJ forge (i.e., the equivalent of Sourcehut)?
> more powerful than git

> not missing out on power

Two very different claims, and it only makes me more skeptical.

Say you start on Main, then make a new branch that you intend to be a PR someday. You make commit 1. Then another. Maybe 6 more. Now you realize that something in commit 1 should have been done differently. So, you "edit" commit 1. All the other commits automatically rebase on top and when you go back to your last commit, it's there. Same with _after_ you PR and someone notices something in commit 3. Edit it, push, and it's fixed.

You can do all that in Git, but I sure as hell never did; and my co-workers really appreciate PRs that are broken into lots of little commits that can be easily looked over, one by one.

You have to force push each time you do this, right? How do your coworkers find the incremental change you made to commit 1 after you force push it, and how do you deal with collaborative branches effectively this way? And if I don't want to work this way and force push, are there other benefits of jj?
the heuristic is 'if you know about rerere and especially if you use it, you should try jj'. if you never force push, you might not see value in jj. (I basically always force push.)
That makes sense, good to know, thanks.

> I basically always force push

How do your colleagues deal with this, or is this mostly on experimental branches or individual projects?

JJ has the concept of "immutable changesets" -- if it sees a commit is referenced from a branch that it's not tracking, it assumes it ought not rebase that commit. Changesets on branches that look like the main branch are immutable too. And you can edit the revset that JJ considers immutable if you need it to be different from the default.

The net effect is that I can change "my" branches as I wish, but I can't change stuff that's been merged or other folks' branches unless I disable the safety features (either using `--ignore-immutable` or tracking the branch).

JJ also makes it really easy to push a single changeset as a branch, which means as you evolve that single commit you can keep the remote updated with your current work really easily. And it's got a specific `jj evolog` command to see how a specific changeset has evolved over time.

It's generally fine if you force push a branch that you're the only one working on. In many projects, there's an expectation that the 'PR Branch' you create in order to make a github pull request is owned by you, and can be rebased/edited/force-pushed at will. It's very common to do things like `git commit --amend --no-edit` to fix a typo or lint issue and then force push to update the last commit.

This has it's problems, and there's a reason things like Geritt are popular in some more sophisticated shops, as they make it much easier to review changes to PRs in response to reviews, as an example.

The PRs are either small enough that it isn’t a problem or large enough that it isn’t a problem… the odd in-between PR experience sucks and it’s one of the cases when I sometimes add more commits instead of force pushing.

+1 to sibling gerrit recommendation; I used to use it a decade ago and it was better then than GitHub PRs today.

People barely ever work off my branches.
IIRC it's push force with lease, ie non destructive push force. No one will be bothered or notice what you did.

And if you have conflicts, it's really easy to rebase and fix any issue.

Okay, sure, but if I realize I should’ve done something differently in commit 1, why wouldn’t I just make a new commit with the fix?
Do you want another person (or yourself in the future) to be able to read your commits, in order, to get a clear account of what changed & why? If so, you should fix up those commits to address mistakes. If not, it doesn’t matter.
Not the OP but for me, no I don't actually.

In a PR branch, my branches usually have a bunch of WIP commits, especially if I've worked on a PR across day boundaries. It's common for more complex PRs that I started down one path and then changed to another path, in which case a lot of work that went into earlier commits is no longer relevant to the picture as a whole.

Once a PR has been submitted for review, I NEVER want to change previous commits and force push, because that breaks common tooling that other team mates rely on to see what changes since their last review. When you do a force push, they now have to review the full PR because they can't be guaranteed exactly which lines changed, and your commit message for the old pr is now muddled.

Once the PR has been merged, I prefer it merged as a single squashed commit so it's reflective of the single atomic PR (because most of the intermediary commits have never actually mattered to debugging a bug caused by a PR).

And if I've already merged a commit to main, then I 100% don't want to rewrite the history of that other commit.

So personally I have never found the commit history of a PR branch useful enough that rewriting past commits was beneficial. The commit history of main is immensely useful, enough that you never want to rewrite that either.

> Once the PR has been merged, I prefer it merged as a single squashed commit so it's reflective of the single atomic PR (because most of the intermediary commits have never actually mattered to debugging a bug caused by a PR).

While working on a maintenance team, most of the projects we handled were on svn where we couldn't squash commits and it as been a huge help enough times that I've turned against blind squashing in general. For example once a bug was introduced during the end-of-work linting cleanup, and a couple times after a code review suggestion. They were in rarely-triggered edge cases (like it came up several years after the code was changed, or were only revealed after a change somewhere else exposed them), but because there was no squash happening afterwards it was easy to look at what should have been happening and quickly fix.

By all means manually squash commits together to clean stuff up, but please keep the types of work separate. Especially once a merge request is opened, changes made from comments on it should not be squashed into the original work.

I wonder by your last comment if this is just is talking past each other.

I try very hard to keep my PRs very focused on one complete unit of work at a time. So when the squash happens that single commit represents one type of change being made to the system.

So when going through history to pinpoint the cause of the big, I can still get what logical change and unit of work caused the change. I don't see the intermediary commits of that unit of work, but I have not personally gotten value out of that level of granularity (especially on team projects where each person's commit practices are different).

If I start working on one PR that starts to contain a refactor or change imthat makes sense to isolate, I'll make that it's own pr that will be squashed.

When you force push a PR, Gitlab shows the changes from the last push. So it also depends which forge you use. I could see that working less well on Github or simpler Git forges
Yeah I don't have much experience outside of GitHub for team projects, so maybe gitlab works better. For GitHub it just gives up and claims it can't give you diff since the last review
Most of the bad modern Git practices summed up in one comment (one atomic, squashed comment).
It'd be more helpful if you explained what exactly is wrong, and what you suggest to do instead.
It’s useful for me to see the mistake and the fix, as it is a good way to jog my memory about the “why” of things. Pristine commit history is not important to me.
Yes, but in that case, I want the fix of the original mistake to be done in a new commit.

Why?

Example #1: - I am working on implementing API calls in the client, made 3 commits and opened a PR - In the meantime, the BE team decides they screwed up and need to update the spec

If I now go and fix it in the commit #1, I lose data. I both lose the version where the API call is in its original state, and I lose the data on what really happened, pretending everything is okay.

Example #2: - I am writing a JVM implementation for our smart-lens - In commit #2 I wrongly implement something, let's say garbage collection, and I release variables after they have 2 references due to a bug. - I am now 6 commits ahead and realise "oh shit wait I have a bug"

If I edit it inline in commit #2, I lose all the knowledge of what the bug was, what the fix is, what even happened or that there was a bug.

tldr: just do an interactive rebase

From what I understand of how jj works, and I’m happy to be corrected because I’m still learning it, is that going back and editing those commits doesn’t change actual original “change” - that is, jj tracks a change ID to everything, and those original commits (once pushed) are immutable. So in theory, with jj, you should be able to see the original commit and the change to fix it, and you can still couple them into a single commit without losing that change history.
You can actually do that in JJ too. And you can take a change that's full of changes to other files, run a single command, and have those changes automatically put into the most recent change (save the one you're working on) that modified it recently.
Some repos merge/pull changes by rebasing them on main and want eventual history not actual history.
I do that in Git all the time. JJ might be easier in some sense but “more powerful” implies that it can do things that are impossible in Git.
JJ has first-class support for conflicted trees, changesets, branches, and operations. The op log itself is a (really useful) feature not present in Git.

You can always end up with the same set of published commits, guaranteed. But the tools you have for manufacturing them and for interacting with their history definitely include things that are possible in JJ but not in Git.

If you're in the middle of a git rebase -i of a stack of 20 commits, and realize while editing commit 15 that you made a mistake at commit 8, how do you go back and edit commit 8 without having to complete the rebase -i?

This is not contrived — this is an entirely realistic scenario that I use jj to handle all the time.

True nested rebase doesn't exist (yet) in Git. What I do is create another commit with the parent commit 8 with commit --fixup and then complete the rebase. The I can just autosquash it, without reediting anything.

You could also keep the rebased commits, abort the rebase, rebase the already rebased commits and then continue the first rebase.

With jj, because it doesn't have modal states of any kind, you can just go back to commit 8, edit it, and everything dependent on it gets auto-rebased. You can also do jj squash --into for a workflow similar to fixup commits.

I would consider the first workflow to be impossible to do by most mere mortals in Git [1]. Meanwhile in jj it's downright trivial.

[1] There technically is a way to do this by setting a temporary branch, aborting the rebase, starting another rebase -i, carefully editing the interactive instructions, going to commit 8, editing that commit, then cherry-picking 9-15 from the temporary branch. But it's too hard to do in practice, and far too easy to get wrong.

> [1] There technically is a way to do this

That's what I've described?

> rebase -i, carefully editing the interactive instructions

You neither need to use interactive rebase nor carefully edit, since there is rebase --onto.

> But it's too hard to do in practice, and far too easy to get wrong.

I do this often it's not more complicated then any other rebase.

What is annoying in Git is rebaseing across multiple merges while forging committer and date information. Can JJ do that better?

I think generally when people say that for jj, they mean it can do the same things with fewer concepts.
The author lists that as a separate benefit, though.

My interpretation is that jj makes certain useful operations convenient to use that would be so complex in git as to be completely impractical. Something like jj undo would be a simple example: jj users can do it, and git users can’t, even though it’s logically possible in both systems.

I do this every day in git. “git rebase -i [hash]” fyi.
you think you do, but you don't; jj edit is much, much better than an edit step in a rebase - it essentially keeps rebasing while you're editing, so you can always see which changes get conflicts, then you are free to resolve them, or not, at your convenience.
So you get all merge conflicts at once? How is that better?
it's exponentially better because you don't need to resolve them until you're ready. conflicts are committed to the local repo like everything else, commits with conflicts are noisily warned about and you can fix them whenever instead of having no other option than immediately.
To the sibling comment that is too deep to reply to, this covers why delayed conflict resolution is advantageous: https://news.ycombinator.com/item?id=45084835

It’s for other branches that hang off the commit that introduced the conflicts.

How does your repo work with conflicts? How does it compile?
You can use all the git commands while doing a rebase.

When you want to work on an older commit for a longer time and don't want to stay in a rebase, you just check it out and work normally, when you are done and want to propagate your changes, then you do a single rebase.

I’m reminded of the Dropbox comment.

You can do anything with a Turing machine. That you can isn’t the point. The point is the tool does all the things you can automatically and correctly so you don’t have to. There’s no ’just do this or that during rebase, or outside of it’. There’s only ‘it rebased everything correctly without a single thought, nice’.

SSH is definitely easier than Dropbox :-).

Yes, and my point is that having a rebase and edit everything isn't too different from first modifying everything and then doing an automatic rebase.

Jj edit isn't even the jj way of doing things. Should be jj new. Unless you have changes stacked after then you'd do jj new -A. And squish when you're done
As a relatively new jj user, I'm curious. Why is the jj new -A + squash better than just a jj edit?
My personal opinion: `jj new` is better because it's non-modal. If you use `jj edit`, you're sort of switching to "edit mode": any change you make will trigger a rebase of all descendants.[1] You're live-mutating the core graph structure rather than a harmless appendage node. Also, if you notice something else that needs to be fixed, you can do it but then you'll need to remember to split it out into a separate commit before leaving edit mode.

With `jj new` + `jj squash`[2], you're collecting work that you can review as a separate thing anytime as you go along. You don't have to remember anything. If you throw in an unrelated change, you'll notice it if you review the changes before squashing them, so you can split it out then. And I'm pretty much always working in this state even when I'm at the top of my branch, so `jj new some-deep-node` doesn't really change anything. If I get called away and have no memory of what I was doing when I return, it doesn't matter: my jj state tells me exactly where things are and what I was doing.

[1] Which is not a huge problem, you have deferred conflict resolution so if something goes wrong you can probably just repair it with normal editing or your editor's undo functionality.

[2] I don't usually bother with `jj new -A`, since I'm going to squash my "out of line" temporary commit into the linear chain anyway. `jj new -A` is more similar to `jj edit` than `jj new` -- it shares some but not all of the modal disadvantages. So perhaps my answer to your actual question is: "yeah, I dunno either."

I forget where I read it (maybe from Martin), but one reason I like to `jj new` before I start any work is just because it makes it easy to revert or abandon if I don't end up liking it. And also easy to diff. `jj new` is pretty much 'free' anyway, every time you make an edit you're creating new commits (not changes!) anyway.
Separation of concerns and performance; when you edit, the commit in the middle of the branch is your working copy and you’ll update the whole branch unnecessarily many times vs just once when you’re on a logical checkpoint.
Jujutsu has many Mercurial-style features, one of them being revsets[1] - a set-notation-style DSL for selecting changesets (eg: which ones to log, etc). I have never found anything as powerful as revsets in Git.[2]

[1] https://jj-vcs.github.io/jj/latest/revsets/

[2] https://stackoverflow.com/questions/22520751/what-is-the-git...

Yeah, I'm excited by the mercurial-style features as a mercurial user looking for something to transition to in a world where git has, sadly, become the standard. The revsets were definitely a joy to discover. The main thing I'm hoping they add is mercurial's diff format which, according to the jujutsu dev discussions, is considerably better than git's, and allows for cleaner "absorb" and, apparently, the clearness of mercurial's "hg fa --deleted".

And, well, it's silly, but I do like revnums. It's a compact way to compare changes over time, even if it's only useful for the local repo. Would be nice to have those too.

git-branchless implements revsets for git https://github.com/arxanas/git-branchless/wiki/Reference:-Re...
Git branchless is basically jj as a git subcommand - it's no coincidence that arxanas is also involved in jj's development!
I agree. I'm willing to give them the benefit of the doubt to some extent because existing Git UIs are pretty poor in my opinion. But I'd like to see some more meat on the bone, in particular a demonstration of why this is easier/more powerful/more convenient to use than the alternatives.
The main thing that makes it more powerful imo is that you can accomplish insane rebases with 1 command that would be really difficult with git.

Like let’s say you have 4 separate PRs in review that have no dependency on each other. You then work on new stuff on top of an octopus merge of all 4. You are exploring different approaches to a solution so you have several anonymous branches where you have tried different things. You want to rebase on master, so you just run jj rebase -d master. All 4 PR branches, the octopus merge, the anonymous branches, they all get rebased with that 1 command. If there are conflicts the first class conflicts mean that you can fix the conflicts whenever you want. If one of your experimental anonymous branches is in conflict but you are unlikely to go with that approach, just leave it in a conflicted state unless you change your mind that you want to actually go that direction.

One example: Merge conflicts can be submitted as a proper entry and dealt with later: https://jj-vcs.github.io/jj/latest/conflicts/
It's also quickly followed by:

> Jujutsu is relatively new and doesn't cover 100% of the features of Git yet.

So it's more powerful except when it's not.

Other do a lot of nitpicking in workflows (with responses that are expected, like "but who cares" or "in git I could do the same"), but not answer this:

JJ is MORE powerful than git because has a BETTER SEMANTICS & ABSTRACTION.

That its. Is like when git emerge, it was more powerful than svn because was distributed.

I wanna make the point clear: Is NOT about the "amount of features or specific workflows" that with pain can be made on git and with effort could be retrofitted on jj eventually (if today are missed, like a equivalent of GitHub!).

The power is what abstraction made jj that is different to git: We work on "commits" all the time, and not need to manually sync the state. Everything derive from this.

And because is a better abstraction, it make more sense and is easier to understand.

The UX derive from this.