Jujutsu for everyone

Another question for jj people: one concrete thing I find annoying with Git is that it's completely incapable or rebasing anything with merge commits. Can jj do this? Even very simple merges are too much for git to rebase. It's especially annoying with `git subtree`. If I want to rebase anything to do with that I don't bother now - I just start again from scratch.

Yes. I have one repository, which is a fork of an OSS project, with a 7-way octopus merge of various patches I carry, and another 2-way merge on top of that one. Every week or two I pull the latest changes from upstream and I rebase all 9+ branches in a single command. If there are conflicts on any one of the parallel streams of work, I can trivially fix each conflict individually in any order I want.

Jujutsu does not treat merge commits any more or less special than non-merge "1-parent" commits. (We used to do this, actually, and occasionally special case merges, but most users found it very confusing.) This regularity means most commands work fine on merges. 'jj new X' is a new commit on top of X. 'jj new X Y' is a merge commit with X and Y as parents. 'jj new X Y Z...' is a 3-way merge, and so on and so forth for any number of commits. Similarly, 'jj rebase' can handle moving commits and preserving the graph structure no matter how many edges are involved in particular, and can add or remove parents from a given commit. This means that conceptually the jj commit graph is merely a simple, ordinary DAG, and operations are transformations on the DAG like you expect.

Actually, this exact workflow is beloved by many community members, and I guess I can take responsibility for popularizing it originally, the "Mega Merge" technique. Instant, easy rebase is an essential part of making this technique viable.

- https://ofcr.se/jujutsu-merge-workflow - https://v5.chriskrycho.com/journal/jujutsu-megamerges-and-jj...

To reinforce the sibling reply with a concrete example:

Let's say you've got a few feature branches, all based of the trunk branch.

  $ jj
  @  ozywpwxm samfredrickson@gmail.com 2025-08-31 13:21:59 b2f1364d
  │  (empty) (no description set)
  │ ○  qxoklwxv samfredrickson@gmail.com 2025-08-31 13:21:27 9cda0936
  ├─╯  (empty) Feature C
  │ ○  ukqynvts samfredrickson@gmail.com 2025-08-31 13:21:26 ceee7029
  ├─╯  (empty) Feature B
  │ ○  nwtxnvxp samfredrickson@gmail.com 2025-08-31 13:21:24 9ccbedf6
  ├─╯  (empty) Feature A
  ◆  yxuvtolz samfredrickson@gmail.com 2025-08-27 09:49:16 master git_head() 8e80b150
  │  Update Claude Code to 1.0.93.

One neat workflow supported by Jujutsu is "working on all branches at the same time."

  $ jj new q u n
  Working copy  (@) now at: zzxxqlzr fb73d4dc (empty) (no description set)
  Parent commit (@-)      : qxoklwxv 9cda0936 (empty) Feature C
  Parent commit (@-)      : ukqynvts ceee7029 (empty) Feature B
  Parent commit (@-)      : nwtxnvxp 9ccbedf6 (empty) Feature A
  $ jj
  @      rzouzmyw samfredrickson@gmail.com 2025-08-31 13:25:56 fb73d4dc
  ├─┬─╮  (empty) (no description set)
  │ │ ○  nwtxnvxp samfredrickson@gmail.com 2025-08-31 13:21:24 9ccbedf6
  │ │ │  (empty) Feature A
  │ ○ │  ukqynvts samfredrickson@gmail.com 2025-08-31 13:21:26 ceee7029
  │ ├─╯  (empty) Feature B
  ○ │  qxoklwxv samfredrickson@gmail.com 2025-08-31 13:21:27 git_head() 9cda0936
  ├─╯  (empty) Feature C
  ◆  yxuvtolz samfredrickson@gmail.com 2025-08-27 09:49:16 master 8e80b150
  │  Update Claude Code to 1.0.93.
  ~

Now you can use the merge revision as a scratch space, and then squash changes from it into one of the feature revisions.

  $ vim README.md
  $ jj squash --into n
  Working copy  (@) now at: rzouzmyw 30ff9b0f (empty) (no description set)
  Parent commit (@-)      : qxoklwxv 9cda0936 (empty) Feature C
  Parent commit (@-)      : ukqynvts ceee7029 (empty) Feature B
  Parent commit (@-)      : nwtxnvxp fb3cca28 Feature A
  $ jj
  @      rzouzmyw samfredrickson@gmail.com 2025-08-31 13:27:41 30ff9b0f
  ├─┬─╮  (empty) (no description set)
  │ │ ○  nwtxnvxp samfredrickson@gmail.com 2025-08-31 13:27:41 fb3cca28
  │ │ │  Feature A
  │ ○ │  ukqynvts samfredrickson@gmail.com 2025-08-31 13:21:26 ceee7029
  │ ├─╯  (empty) Feature B
  ○ │  qxoklwxv samfredrickson@gmail.com 2025-08-31 13:21:27 git_head() 9cda0936
  ├─╯  (empty) Feature C
  ◆  yxuvtolz samfredrickson@gmail.com 2025-08-27 09:49:16 master 8e80b150
  │  Update Claude Code to 1.0.93.

Later, you decide to fetch changes from your remote, and notice that your revisions are based on an out-of-date version of the trunk.

  $ jj git fetch
  remote: Enumerating objects: 17, done.
  remote: Total 12 (delta 6), reused 0 (delta 0), pack-reused 0
  bookmark: master@origin [updated] tracked
  $ jj
  @      rzouzmyw samfredrickson@gmail.com 2025-08-31 13:27:41 30ff9b0f
  ├─┬─╮  (empty) (no description set)
  │ │ ○  nwtxnvxp samfredrickson@gmail.com 2025-08-31 13:27:41 fb3cca28
  │ │ │  Feature A
  │ ○ │  ukqynvts samfredrickson@gmail.com 2025-08-31 13:21:26 ceee7029
  │ ├─╯  (empty) Feature B
  ○ │  qxoklwxv samfredrickson@gmail.com 2025-08-31 13:21:27 git_head() 9cda0936
  ├─╯  (empty) Feature C
  │ ◆  zvpmmzru samfredrickson@gmail.com 2025-08-29 15:59:55 master 658a3d12
  │ │  Update Claude Code to 1.0.98.
  │ ~  (elided revisions)
  ├─╯
  ◆  yxuvtolz samfredrickson@gmail.com 2025-08-27 09:49:16 8e80b150
  │  Update Claude Code to 1.0.93.
  ~

With Jujutsu, you can run one command to rebase _everything_ against the latest trunk revision.

  $ jj rebase -s 'roots(trunk()..mutable())' -d 'trunk()'
  Rebased 4 commits to destination
  Working copy  (@) now at: rzouzmyw 88ed8085 (empty) (no description set)
  Parent commit (@-)      : qxoklwxv 005442c3 (empty) Feature C
  Parent commit (@-)      : ukqynvts 23923cf2 (empty) Feature B
  Parent commit (@-)      : nwtxnvxp 769d0539 Feature A
  Added 0 files, modified 2 files, removed 0 files
  $ jj
  @      rzouzmyw samfredrickson@gmail.com 2025-08-31 13:32:08 88ed8085
  ├─┬─╮  (empty) (no description set)
  │ │ ○  nwtxnvxp samfredrickson@gmail.com 2025-08-31 13:32:08 769d0539
  │ │ │  Feature A
  │ ○ │  ukqynvts samfredrickson@gmail.com 2025-08-31 13:32:08 23923cf2
  │ ├─╯  (empty) Feature B
  ○ │  qxoklwxv samfredrickson@gmail.com 2025-08-31 13:32:08 git_head() 005442c3
  ├─╯  (empty) Feature C
  ◆  zvpmmzru samfredrickson@gmail.com 2025-08-29 15:59:55 master 658a3d12
  │  Update Claude Code to 1.0.98.
  ~

I use this command so much that it's aliased as "jjsr", "Jujutsu Super Rebase".

What does git rebase --rebase-merges do in this case? How does it botch up the repo?

A commit with multiple parents is called a merge commit. :-)

The "super rebase" seams to be nice though. However I just tested it and achieved the same with git rebase --rebase-merges --update-refs. Have I missed something?

Jujutsu distinguishes between "revisions" and "commits." Revision IDs like "rzouzmyw" stay stable, whereas commit IDs of course change with the content. You can see in my example how the commits associated with a revision change over time: rzouzmyw starts as fb73d4dc, then 30ff9b0f, and finally 88ed8085. I used "merge revision" to by consistent with Jujutsu's terminology.

Anyway, I just tried that command you suggested, but it didn't seem to work?

  $ jj new
  $ jj bookmark create woot -r @-
  $ jj
  @  wxkrvmxs samfredrickson@gmail.com 2025-08-31 14:53:19 4bbb7f5a
  │  (empty) (no description set)
  ○      rzouzmyw samfredrickson@gmail.com 2025-08-31 13:27:41 woot git_head() 30ff9b0f
  ├─┬─╮  (empty) (no description set)
  │ │ ○  nwtxnvxp samfredrickson@gmail.com 2025-08-31 13:27:41 fb3cca28
  │ │ │  Feature A
  │ ○ │  ukqynvts samfredrickson@gmail.com 2025-08-31 13:21:26 ceee7029
  │ ├─╯  (empty) Feature B
  ○ │  qxoklwxv samfredrickson@gmail.com 2025-08-31 13:21:27 9cda0936
  ├─╯  (empty) Feature C
  │ ◆  zvpmmzru samfredrickson@gmail.com 2025-08-29 15:59:55 master 658a3d12
  │ │  Update Claude Code to 1.0.98.
  │ ~  (elided revisions)
  ├─╯
  ◆  yxuvtolz samfredrickson@gmail.com 2025-08-27 09:49:16 8e80b150
  │  Update Claude Code to 1.0.93.
  ~
  $ git checkout woot
  $ git log --graph
  *-.   commit 30ff9b0f274c9adaca4eeadcf21d5e918e4e3578 (HEAD -> woot)
  |\ \  Merge: 9cda093 ceee702 fb3cca2
  | | | Author: Sam Fredrickson <samfredrickson@gmail.com>
  | | | Date:   Sun Aug 31 13:27:41 2025 -0700
  | | |
  | | * commit fb3cca2823b4dffe374b67d28e3c91c206828d47
  | | | Author: Sam Fredrickson <samfredrickson@gmail.com>
  | | | Date:   Sun Aug 31 13:21:24 2025 -0700
  | | |
  | | |     Feature A
  | | |
  | * | commit ceee7029730c49ae30890c1641c7d6645e60fca4
  | |/  Author: Sam Fredrickson <samfredrickson@gmail.com>
  | |   Date:   Sun Aug 31 13:21:26 2025 -0700
  | |
  | |       Feature B
  | |
  * | commit 9cda09363efe257a954b5563ce6af287a506d808
  |/  Author: Sam Fredrickson <samfredrickson@gmail.com>
  |   Date:   Sun Aug 31 13:21:27 2025 -0700
  |
  |       Feature C
  |
  * commit 8e80b15010c4d9373c5828fdf8a83c53df75ec00
  | Author: Sam Fredrickson <samfredrickson@gmail.com>
  | Date:   Wed Aug 27 09:48:45 2025 -0700
  |
  |     Update Claude Code to 1.0.93.
  $ git rebase --rebase-merges --update-refs master
  Trying simple merge with cfa85486fa3d53401be518cb42936fb6fd3c128c
  Trying simple merge with ffebef1cb34ca1670b48c594b2014e71be7d1b2b
  error: Empty commit message.
  Not committing merge; use 'git commit' to complete the merge.
  Could not apply 30ff9b0... rev-ceee702 rev-fb3cca2 #
  $ git status
  interactive rebase in progress; onto 658a3d1
  Last commands done (10 commands done):
     pick 9cda093 # Feature C # empty
     merge -C 30ff9b0f274c9adaca4eeadcf21d5e918e4e3578 rev-ceee702 rev-fb3cca2 #
    (see more in file .git/rebase-merge/done)
  No commands remaining.
  
  All conflicts fixed but you are still merging.
    (use "git commit" to conclude merge)
  
  Changes to be committed:
          modified:   README.md
  $ jj
  Reset the working copy parent to the new Git HEAD.
  @  tymwqlyq samfredrickson@gmail.com 2025-08-31 14:57:22 d083f61e
  │  (no description set)
  ○  vmnnlqro samfredrickson@gmail.com 2025-08-31 14:56:55 git_head() f92f7505
  │  (empty) Feature C
  ◆  zvpmmzru samfredrickson@gmail.com 2025-08-29 15:59:55 master 658a3d12
  │  Update Claude Code to 1.0.98.
  ~  (elided revisions)
  │ ○      rzouzmyw samfredrickson@gmail.com 2025-08-31 13:27:41 woot 30ff9b0f
  │ ├─┬─╮  (empty) (no description set)
  │ │ │ ○  nwtxnvxp samfredrickson@gmail.com 2025-08-31 13:27:41 fb3cca28
  ├─────╯  Feature A
  │ │ ○  ukqynvts samfredrickson@gmail.com 2025-08-31 13:21:26 ceee7029
  ├───╯  (empty) Feature B
  │ ○  qxoklwxv samfredrickson@gmail.com 2025-08-31 13:21:27 9cda0936
  ├─╯  (empty) Feature C
  ◆  yxuvtolz samfredrickson@gmail.com 2025-08-27 09:49:16 8e80b150
  │  Update Claude Code to 1.0.93.
  ~

Maybe I'm using the git command incorrectly?

Also, though, I'm assuming that git command will only rebase the branch you have currently checked out, whereas the jj command I gave will rebase _everything_, not just revisions that are parents of HEAD.

Edit: I figured out my issue. Git doesn't like empty commits & merge commits with no description. After addressing that, then the `git rebase --rebase-merges --update-refs master` command worked.

There's still the caveat though that the Git command will only rebase the "woot" branch. If I had some other "feature D" commit that wasn't included in "woot", that commit wouldn't be rebased. But the `jjsr` command would see and rebase that commit as well.

  $ jj
  @  qsvwusnk samfredrickson@gmail.com 2025-08-31 16:17:35 6fd02707
  │  (empty) (no description set)
  ○      rzouzmyw samfredrickson@gmail.com 2025-08-31 16:17:35 woot git_head() e6d64886
  ├─┬─╮  (empty) Merge
  │ │ ○  nwtxnvxp samfredrickson@gmail.com 2025-08-31 13:27:41 fb3cca28
  │ │ │  Feature A
  │ ○ │  ukqynvts samfredrickson@gmail.com 2025-08-31 16:16:36 9957dca2
  │ ├─╯  Feature B
  ○ │  qxoklwxv samfredrickson@gmail.com 2025-08-31 16:16:44 4361de8b
  ├─╯  Feature C
  │ ○  nwoxyzlx samfredrickson@gmail.com 2025-08-31 16:14:42 ce8de62d
  ├─╯  Feature D
  │ ◆  zvpmmzru samfredrickson@gmail.com 2025-08-29 15:59:55 master 658a3d12
  │ │  Update Claude Code to 1.0.98.
  │ ~  (elided revisions)
  ├─╯
  ◆  yxuvtolz samfredrickson@gmail.com 2025-08-27 09:49:16 8e80b150
  │  Update Claude Code to 1.0.93.
  ~
  
  $ git checkout woot
  Switched to branch 'woot'
  
  $ git rebase --rebase-merges --update-refs master
  Trying simple merge with f339926f729437f78ac407c28fc84ce3b0441eb7
  Trying simple merge with 4372b2c4f538164a10bb9d8e81899bf61eeecaf2
  Merge made by the 'octopus' strategy.
  Successfully rebased and updated refs/heads/woot.
  
  $ jj
  Reset the working copy parent to the new Git HEAD.
  Abandoned 4 commits that are no longer reachable.
  Done importing changes from the underlying Git repo.
  @  zlxqyrmq samfredrickson@gmail.com 2025-08-31 16:17:59 970c80f8
  │  (empty) (no description set)
  ○      qumulkxr samfredrickson@gmail.com 2025-08-31 16:17:42 woot git_head() cc189c82
  ├─┬─╮  (empty) Merge
  │ │ ○  vkuwsssr samfredrickson@gmail.com 2025-08-31 16:17:42 4372b2c4
  │ │ │  Feature A
  │ ○ │  lmsrxxzm samfredrickson@gmail.com 2025-08-31 16:17:42 f339926f
  │ ├─╯  Feature B
  ○ │  wrsnrokn samfredrickson@gmail.com 2025-08-31 16:17:42 53ec4dc0
  ├─╯  Feature C
  ◆  zvpmmzru samfredrickson@gmail.com 2025-08-29 15:59:55 master 658a3d12
  │  Update Claude Code to 1.0.98.
  ~  (elided revisions)
  │ ○  nwoxyzlx samfredrickson@gmail.com 2025-08-31 16:14:42 ce8de62d
  ├─╯  Feature D
  ◆  yxuvtolz samfredrickson@gmail.com 2025-08-27 09:49:16 8e80b150
  │  Update Claude Code to 1.0.93.
  ~

Versus:

  $ jjsr
  Rebased 6 commits to destination
  Working copy  (@) now at: qsvwusnk e793b1e4 (empty) (no description set)
  Parent commit (@-)      : rzouzmyw 3927be34 woot | (empty) Merge
  Added 0 files, modified 2 files, removed 0 files
  
  $ jj
  @  qsvwusnk samfredrickson@gmail.com 2025-08-31 16:18:58 e793b1e4
  │  (empty) (no description set)
  ○      rzouzmyw samfredrickson@gmail.com 2025-08-31 16:18:58 woot git_head() 3927be34
  ├─┬─╮  (empty) Merge
  │ │ ○  nwtxnvxp samfredrickson@gmail.com 2025-08-31 16:18:58 12f659cf
  │ │ │  Feature A
  │ ○ │  ukqynvts samfredrickson@gmail.com 2025-08-31 16:18:58 5c0ce98f
  │ ├─╯  Feature B
  ○ │  qxoklwxv samfredrickson@gmail.com 2025-08-31 16:18:58 f9f217e8
  ├─╯  Feature C
  │ ○  nwoxyzlx samfredrickson@gmail.com 2025-08-31 16:18:58 373d6ab1
  ├─╯  Feature D
  ◆  zvpmmzru samfredrickson@gmail.com 2025-08-29 15:59:55 master 658a3d12
  │  Update Claude Code to 1.0.98.
  ~

True, Git only rebases from one branch. You would need run the same command on all other branches, or use git for-each-ref.

I can't remember exactly but I have tried it a couple of times and couldn't get it to work at all.