jj/docs/tutorial.md

# Tutorial

> **Hint:** This tutorial has become somewhat out of date. Many people find
> the alternative (not quite finished) [tutorial by Steve
> Klabnik](https://steveklabnik.github.io/jujutsu-tutorial/) helpful.

This text assumes that the reader is familiar with Git.

## Preparation

If you haven't already, make sure you
[install and configure Jujutsu](install-and-setup.md).

## Cloning a Git repository

> **Hint:** Most identifiers used in this tutorial will be different when you
> try this at home!

Let's start by cloning GitHub's Hello-World repo using `jj`:

```shell
# Note the "git" before "clone" (there is no support for cloning native jj
# repos yet)
$ jj git clone https://github.com/octocat/Hello-World
Fetching into new repo in "/tmp/tmp.O1DWMiaKd4/Hello-World"
remote: Enumerating objects: 13, done.
remote: Total 13 (delta 0), reused 0 (delta 0), pack-reused 13 (from 1)
bookmark: master@origin          [new] untracked
bookmark: octocat-patch-1@origin [new] untracked
bookmark: test@origin            [new] untracked
Setting the revset alias `trunk()` to `master@origin`
Working copy  (@) now at: kntqzsqt d7439b06 (empty) (no description set)
Parent commit (@-)      : orrkosyo 7fd1a60b master | (empty) Merge pull request #6 from Spaceghost/patch-1
Added 1 files, modified 0 files, removed 0 files
$ cd Hello-World
```

Running `jj st` (short for `jj status`) now yields something like this:

```shell
$ jj st
The working copy has no changes.
Working copy  (@) : kntqzsqt d7439b06 (empty) (no description set)
Parent commit (@-): orrkosyo 7fd1a60b master | (empty) Merge pull request #6 from Spaceghost/patch-1
```

Let's look at that output as it introduces new concepts. You can see two
commits: Parent and working copy. Both are identified using two separate
identifiers: the "change ID" and the "commit ID".

The parent commit, for example, has the change ID `orrkosyo` and the commit ID
`7fd1a60b`.

> **Git users:** The commit ID/hash is what you're used to from Git and should
> match what you see when you look at the repository using `git log` in a Git
> checkout of the repository.
> The change ID however, is a new concept, unique to Jujutsu.

We can also see from the output above that our working copy is an actual commit
with a commit ID (`d7439b06` in the example). When you make a change in the
working copy, the working-copy commit gets automatically amended by the next
`jj` command.

> **Git users:** This is a huge difference from Git where the working copy is a
> separate concept and not yet a commit.

## Changes

A change is a commit that can evolve while keeping a stable identifier (similar
to Gerrit's Change-Id). In other words: You can make changes to files in a
change, resulting in a new commit hash, but the change ID will remain the same.

You can see that our clone operation automatically created a new change:

```shell
Working copy  (@) : kntqzsqt d7439b06 (empty) (no description set)
```

This new change has the ID `kntqzsqt` and it is currently empty (contains no
changes compared to the parent) and has no description.

## Creating our first change

Let's say we want to edit the `README` file in the repo to say "Goodbye"
instead of "Hello". Start by describing the change (adding a commit message) so
we don't forget what we're working on:

```shell
# This brings up $EDITOR (or `pico` or `Notepad` by default).
# Enter something like "Say goodbye" in the editor and then save the file and close
# the editor.
$ jj describe
Working copy  (@) now at: kntqzsqt e427edcf (empty) Say goodbye
Parent commit (@-)      : orrkosyo 7fd1a60b master | (empty) Merge pull request #6 from Spaceghost/patch-1
```

Now make the change in the README:

```shell
# Adjust as necessary for compatibility with your flavor of `sed`
$ sed -i 's/Hello/Goodbye/' README
$ jj st
Working copy changes:
M README
Working copy  (@) : kntqzsqt 5d39e19d Say goodbye
Parent commit (@-): orrkosyo 7fd1a60b master | (empty) Merge pull request #6 from Spaceghost/patch-1
```

Note that you didn't have to tell Jujutsu to add the change like you would with
`git add`. You actually don't even need to tell it when you add new files or
remove existing files. To untrack a path, add it to your `.gitignore` and run
`jj file untrack <path>`.

Also note that the commit hash for our current change (`kntqzsqt`) changed from
`e427edcf` to `5d39e19d`!

To see the diff, run `jj diff`:

```shell
$ jj diff --git  # Feel free to skip the `--git` flag
diff --git a/README b/README
index 980a0d5f19..1ce3f81130 100644
--- a/README
+++ b/README
@@ -1,1 +1,1 @@
-Hello World!
+Goodbye World!
```

Jujutsu's diff format currently defaults to inline coloring of the diff (like
`git diff --color-words`), so we used `--git` above to make the diff readable in
this tutorial.

As you may have noticed, the working-copy commit's ID changed both when we
edited the description and when we edited the README. However, the parent commit
stayed the same. Each change to the working-copy commit amends the previous
version. So how do we tell Jujutsu that we are done amending the current change
and want to start working on a new one? That is what `jj new` is for. That will
create a new commit on top of your current working-copy commit. The new commit
is for the working-copy changes.

So, let's say we're now done with this change, so we create a new change:

```shell
$ jj new
Working copy  (@) now at: mpqrykyp aef4df99 (empty) (no description set)
Parent commit (@-)      : kntqzsqt 5d39e19d Say goodbye
$ jj st
The working copy has no changes.
Working copy  (@) : mpqrykyp aef4df99 (empty) (no description set)
Parent commit (@-): kntqzsqt 5d39e19d Say goodbye
```

If we later realize that we want to make further changes, we can make them in
the working copy and then run `jj squash`. That command squashes (moves) the
changes from a given commit into its parent commit. Like most commands, it acts
on the working-copy commit by default. When run on the working-copy commit, it
behaves very similar to `git commit --amend`.

Alternatively, we can use `jj edit <commit>` to resume editing a commit in the
working copy. Any further changes in the working copy will then amend the
commit. Whether you choose to create a new change and squash, or to edit,
typically depends on how done you are with the change; if the change is almost
done, it makes sense to use `jj new` so you can easily review your adjustments
with `jj diff` before running `jj squash`.

To view how a change has evolved over time, we can use `jj evolog` to see each
recorded change for the current commit. This records changes to the working
copy, message, squashes, rebases, etc.

## The log command and "revsets"

You're probably familiar with `git log`. Jujutsu has very similar functionality
in its `jj log` command:

```shell
$ jj log
@  mpqrykyp martinvonz@google.com 2023-02-12 15:00:22 aef4df99
│  (empty) (no description set)
○  kntqzsqt martinvonz@google.com 2023-02-12 14:56:59 5d39e19d
│  Say goodbye
◆  orrkosyo octocat@nowhere.com 2012-03-06 15:06:50 master 7fd1a60b
│  (empty) Merge pull request #6 from Spaceghost/patch-1
~
```

The `@` indicates the working-copy commit. The first ID on a line
(e.g. "mpqrykyp" above) is the change ID. The second ID is the commit ID. You
can give either ID to commands that take revisions as arguments. We will
generally prefer change IDs because they stay the same when the commit is
rewritten.

By default, `jj log` lists your local commits, with some remote commits added
for context. The `~` indicates that the commit has parents that are not included
in the graph. We can use the `--revisions`/`-r` flag to select a different set
of revisions to list. The flag accepts a ["revset"](revsets.md), which is an
expression in a simple language for specifying revisions. For example, `@`
refers to the working-copy commit, `root()` refers to the root commit,
`bookmarks()` refers to all commits pointed to by bookmarks (similar to Git's
branches). We can combine expressions with `|` for union, `&` for intersection
and `~` for difference. For example:

```shell
$ jj log -r '@ | root() | bookmarks()'
@  mpqrykyp martinvonz@google.com 2023-02-12 15:00:22 aef4df99
│  (empty) (no description set)
~  (elided revisions)
◆  orrkosyo octocat@nowhere.com 2012-03-06 15:06:50 master 7fd1a60b
│  (empty) Merge pull request #6 from Spaceghost/patch-1
~  (elided revisions)
◆  zzzzzzzz root() 00000000
```

The `00000000` commit (change ID `zzzzzzzz`) is a virtual commit that's called
the "root commit". It's the root commit of every repo. The `root()`
function in the revset matches it.

There are also operators for getting the parents (`foo-`), children (`foo+`),
ancestors (`::foo`), descendants (`foo::`), DAG range (`foo::bar`, like
`git log --ancestry-path`), range (`foo..bar`, same as Git's). See
[the revset documentation](revsets.md) for all revset operators and functions.

> **Hint:** If the default `jj log` omits some commits you expect to see, you
> can always run `jj log -r ::` (or, equivalently, `jj log -r 'all()'`) to see
> all the commits.

## Conflicts

Now let's see how Jujutsu deals with merge conflicts. We'll start by making some
commits. We use `jj new` with the `--message`/`-m` option to set change
descriptions (commit messages) right away.

```shell
# Start creating a chain of commits off of the `master` bookmark
$ jj new master -m A; echo a > file1
Working copy  (@) now at: nuvyytnq 00a2aeed (empty) A
Parent commit (@-)      : orrkosyo 7fd1a60b master | (empty) Merge pull request #6 from Spaceghost/patch-1
Added 0 files, modified 1 files, removed 0 files
$ jj new -m B1; echo b1 > file1
Working copy  (@) now at: ovknlmro 967d9f9f (empty) B1
Parent commit (@-)      : nuvyytnq 5dda2f09 A
$ jj new -m B2; echo b2 > file1
Working copy  (@) now at: puqltutt 8ebeaffa (empty) B2
Parent commit (@-)      : ovknlmro 7d7c6e6b B1
$ jj new -m C; echo c > file2
Working copy  (@) now at: qzvqqupx 62a3c6d3 (empty) C
Parent commit (@-)      : puqltutt daa6ffd5 B2
$ jj log
@  qzvqqupx martinvonz@google.com 2023-02-12 15:07:41 2370ddf3
│  C
○  puqltutt martinvonz@google.com 2023-02-12 15:07:33 daa6ffd5
│  B2
○  ovknlmro martinvonz@google.com 2023-02-12 15:07:24 7d7c6e6b
│  B1
○  nuvyytnq martinvonz@google.com 2023-02-12 15:07:05 5dda2f09
│  A
│ ○  kntqzsqt martinvonz@google.com 2023-02-12 14:56:59 5d39e19d
├─╯  Say goodbye
◆  orrkosyo octocat@nowhere.com 2012-03-06 15:06:50 master 7fd1a60b
│  (empty) Merge pull request #6 from Spaceghost/patch-1
~
```

We now have a few commits, where A, B1, and B2 modify the same file, while C
modifies a different file. Let's now rebase B2 directly onto A. We use the
`--source`/`-s` option on the change ID of B2, and `--destination`/`-d` option
on A.

```shell
$ jj rebase -s puqltutt -d nuvyytnq  # Replace the IDs by what you have for B2 and A
Rebased 2 commits to destination
Working copy  (@) now at: qzvqqupx 1978b534 (conflict) C
Parent commit (@-)      : puqltutt f7fb5943 (conflict) B2
Added 0 files, modified 1 files, removed 0 files
Warning: There are unresolved conflicts at these paths:
file1    2-sided conflict
New conflicts appeared in 2 commits:
  qzvqqupx 1978b534 (conflict) C
  puqltutt f7fb5943 (conflict) B2
Hint: To resolve the conflicts, start by updating to the first one:
  jj new puqltutt
Then use `jj resolve`, or edit the conflict markers in the file directly.
Once the conflicts are resolved, you may want to inspect the result with `jj diff`.
Then run `jj squash` to move the resolution into the conflicted commit.

$ jj log
@  qzvqqupx martinvonz@google.com 2023-02-12 15:08:33 1978b534 conflict
│  C
×  puqltutt martinvonz@google.com 2023-02-12 15:08:33 f7fb5943 conflict
│  B2
│ ○  ovknlmro martinvonz@google.com 2023-02-12 15:07:24 7d7c6e6b
├─╯  B1
○  nuvyytnq martinvonz@google.com 2023-02-12 15:07:05 5dda2f09
│  A
│ ○  kntqzsqt martinvonz@google.com 2023-02-12 14:56:59 5d39e19d
├─╯  Say goodbye
◆  orrkosyo octocat@nowhere.com 2012-03-06 15:06:50 master 7fd1a60b
│  (empty) Merge pull request #6 from Spaceghost/patch-1
~
```

There are several things worth noting here. First, the `jj rebase` command said
"Rebased 2 commits". That's because we asked it to rebase commit B2 with the
`-s` option, which also rebases descendants (commit C in this case). Second,
because B2 modified the same file (and word) as B1, rebasing it resulted in
conflicts, as the output indicates. Third, the conflicts did not prevent the
rebase from completing successfully, nor did it prevent C from getting rebased
on top.

Now let's resolve the conflict in B2. We'll do that by creating a new commit on
top of B2. Once we've resolved the conflict, we'll squash the conflict
resolution into the conflicted B2. That might look like this:

```shell
$ jj new puqltutt  # Replace the ID by what you have for B2
Working copy  (@) now at: zxoosnnp c7068d1c (conflict) (empty) (no description set)
Parent commit (@-)      : puqltutt f7fb5943 (conflict) B2
Added 0 files, modified 0 files, removed 1 files
Warning: There are unresolved conflicts at these paths:
file1    2-sided conflict

$ jj st
The working copy has no changes.
Working copy  (@) : zxoosnnp c7068d1c (conflict) (empty) (no description set)
Parent commit (@-): puqltutt f7fb5943 (conflict) B2
Warning: There are unresolved conflicts at these paths:
file1    2-sided conflict
Hint: To resolve the conflicts, start by updating to it:
  jj new puqltutt
Then use `jj resolve`, or edit the conflict markers in the file directly.
Once the conflicts are resolved, you may want to inspect the result with `jj diff`.
Then run `jj squash` to move the resolution into the conflicted commit.

$ cat file1
<<<<<<< Conflict 1 of 1
%%%%%%% Changes from base to side #1
-b1
+a
+++++++ Contents of side #2
b2
>>>>>>> Conflict 1 of 1 ends

$ echo resolved > file1

$ jj st
Working copy changes:
M file1
Working copy  (@) : zxoosnnp c2a31a06 (no description set)
Parent commit (@-): puqltutt f7fb5943 (conflict) B2
Hint: Conflict in parent commit has been resolved in working copy

$ jj squash
Rebased 1 descendant commits
Working copy  (@) now at: ntxxqymr e3c279cc (empty) (no description set)
Parent commit (@-)      : puqltutt 2c7a658e B2
Existing conflicts were resolved or abandoned from 2 commits.

$ jj log
@  ntxxqymr martinvonz@google.com 2023-02-12 19:34:09 e3c279cc
│  (empty) (no description set)
│ ○  qzvqqupx martinvonz@google.com 2023-02-12 19:34:09 b9da9d28
├─╯  C
○  puqltutt martinvonz@google.com 2023-02-12 19:34:09 2c7a658e
│  B2
│ ○  ovknlmro martinvonz@google.com 2023-02-12 15:07:24 7d7c6e6b
├─╯  B1
○  nuvyytnq martinvonz@google.com 2023-02-12 15:07:05 5dda2f09
│  A
│ ○  kntqzsqt martinvonz@google.com 2023-02-12 14:56:59 5d39e19d
├─╯  Say goodbye
◆  orrkosyo octocat@nowhere.com 2012-03-06 15:06:50 master 7fd1a60b
│  (empty) Merge pull request #6 from Spaceghost/patch-1
~
```

Note that commit C automatically got rebased on top of the resolved B2, and that
C is also resolved (since it modified only a different file).

By the way, if we want to get rid of B1 now, we can run `jj abandon
ovknlmro`. That will hide the commit from the log output and will rebase any
descendants to its parent.

## The operation log

Jujutsu keeps a record of all changes you've made to the repo in what's called
the "operation log". Use the `jj op` (short for `jj operation`) family of
commands to interact with it. To list the operations, use `jj op log`:

```shell
$ jj op log
@  d3b77addea49 martinvonz@vonz.svl.corp.google.com 3 minutes ago, lasted 3 milliseconds
│  squash commits into 63874fe6c4fba405ffc38b0dd926f03b715cf7ef
│  args: jj squash
○  6fc1873c1180 martinvonz@vonz.svl.corp.google.com 3 minutes ago, lasted 1 milliseconds
│  snapshot working copy
│  args: jj st
○  ed91f7bcc1fb martinvonz@vonz.svl.corp.google.com 6 minutes ago, lasted 1 milliseconds
│  new empty commit
│  args: jj new puqltutt
○  367400773f87 martinvonz@vonz.svl.corp.google.com 12 minutes ago, lasted 3 milliseconds
│  rebase commit daa6ffd5a09a8a7d09a65796194e69b7ed0a566d and descendants
│  args: jj rebase --source puqltutt --destination nuvyytnq
[many more lines]
```

The most useful command is `jj undo` (alias for `jj op undo`), which will undo
an operation. By default, it will undo the most recent operation. Let's try it:

```shell
$ jj undo
Undid operation: d3b77addea49 (2025-05-12 00:27:27) squash commits into f7fb5943a6b9460eb106dba2fac5cac1625c6f7a
Working copy  (@) now at: zxoosnnp 63874fe6 (no description set)
Parent commit (@-)      : puqltutt f7fb5943 (conflict) B2
New conflicts appeared in 2 commits:
  qzvqqupx 1978b534 (conflict) C
  puqltutt f7fb5943 (conflict) B2
Hint: To resolve the conflicts, start by updating to the first one:
  jj new nprznkxy
Then use `jj resolve`, or edit the conflict markers in the file directly.
Once the conflicts are resolved, you may want to inspect the result with `jj diff`.
Then run `jj squash` to move the resolution into the conflicted commit.

$ jj log
@  zxoosnnp martinvonz@google.com 2023-02-12 19:34:09 63874fe6
│  (no description set)
│ ×  qzvqqupx martinvonz@google.com 2023-02-12 15:08:33 1978b534 conflict
├─╯  C
×  puqltutt martinvonz@google.com 2023-02-12 15:08:33 f7fb5943 conflict
│  B2
│ ○  ovknlmro martinvonz@google.com 2023-02-12 15:07:24 7d7c6e6b
├─╯  B1
○  nuvyytnq martinvonz@google.com 2023-02-12 15:07:05 5dda2f09
│  A
│ ○  kntqzsqt martinvonz@google.com 2023-02-12 14:56:59 5d39e19d
├─╯  Say goodbye
◆  orrkosyo octocat@nowhere.com 2012-03-06 15:06:50 master 7fd1a60b
│  (empty) Merge pull request #6 from Spaceghost/patch-1
~
```

As you can perhaps see, that undid the `jj squash` invocation we used for
squashing the conflict resolution into commit B2 earlier. Notice that it also
updated the working copy.

You can also view the repo the way it looked after some earlier operation. For
example, if you want to see `jj log` output right after the `jj rebase`
operation, try `jj log --at-op=367400773f87` but use the hash from your own
`jj op log`.

## Moving content changes between commits

You have already seen how `jj squash` can combine the changes from two commits
into one. There are several other commands for changing the contents of existing
commits.

We'll need some more complex content to test these commands, so let's create a
few more commits:

```shell
$ jj new master -m abc; printf 'a\nb\nc\n' > file
Working copy  (@) now at: ztqrpvnw f94e49cf (empty) abc
Parent commit (@-)      : orrkosyo 7fd1a60b master | (empty) Merge pull request #6 from Spaceghost/patch-1
Added 0 files, modified 0 files, removed 1 files

$ jj new -m ABC; printf 'A\nB\nc\n' > file
Working copy  (@) now at: kwtuwqnm 6f30cd1f (empty) ABC
Parent commit (@-)      : ztqrpvnw 51002261 ab

$ jj new -m ABCD; printf 'A\nB\nC\nD\n' > file
Working copy  (@) now at: mrxqplyk a6749154 (empty) ABCD
Parent commit (@-)      : kwtuwqnm 30aecc08 ABC

$ jj log -r master::@
@  mrxqplyk martinvonz@google.com 2023-02-12 19:38:21 b98c607b
│  ABCD
○  kwtuwqnm martinvonz@google.com 2023-02-12 19:38:12 30aecc08
│  ABC
○  ztqrpvnw martinvonz@google.com 2023-02-12 19:38:03 51002261
│  abc
◆  orrkosyo octocat@nowhere.com 2012-03-06 15:06:50 master 7fd1a60b
│  (empty) Merge pull request #6 from Spaceghost/patch-1
~
```

We "forgot" to capitalize "c" in the second commit when we capitalized the other
letters. We then fixed that in the third commit when we also added "D". It would
be cleaner to move the capitalization of "c" into the second commit. We can do
that by running `jj squash` with the `--interactive`/`-i` option on the third
commit. Remember that `jj squash` moves all the changes from one commit into its
parent. `jj squash -i` moves only part of the changes into its parent. Now try
that:

```shell
$ jj squash -i
Hint: Using default editor ':builtin'; run `jj config set --user ui.diff-editor :builtin` to disable this message.
Rebased 1 descendant commits
Working copy  (@) now at: mrxqplyk 52a6c7fd ABCD
Parent commit (@-)      : kwtuwqnm 643061ac ABC
```

That will bring up the built-in diff editor[^alternative_diff_editors] with a
diff of the changes in the "ABCD" commit. Expand the file by clicking on `(+)`
or with right arrow, then select the sections/line to include by clicking or
using space. Once complete, press `c` to confirm changes, or `q` to exit without
saving. You can also use the mouse to click on the menu items to see more
options (keyboard navigation is currently limited).

[^alternative_diff_editors]: There are many other diff editors you could use.
For example, if you have [Meld](https://meldmerge.org) installed and in the
PATH, you can use it via `jj squash -i --tool meld` or a fancier config with `jj
squash -i --tool meld-3`. You can configure the default with the
[`ui.diff-editor` option](config.md#editing-diffs); those docs also explain how
to specify a path to an executable if it is not in the PATH.

If we look at the diff of the second commit, we now see that all three lines got
capitalized:

```shell
$ jj diff -r @- --git
diff --git a/file b/file
index de980441c3..b1e67221af 100644
--- a/file
+++ b/file
@@ -1,3 +1,3 @@
-a
-b
-c
+A
+B
+C
```

The child change ("ABCD" in our case) will have the same content *state* after
the `jj squash` command. That means that you can move any changes you want into
the parent change, even if they touch the same word, and it won't cause any
conflicts.

Let's try one final command for changing the contents of an exiting commit. That
command is `jj diffedit`, which lets you edit the changes in a commit without
checking it out.

```shell
$ jj diffedit -r @-
Hint: Using default editor ':builtin'; run `jj config set --user ui.diff-editor :builtin` to disable this message.
Rebased 1 descendant commits
Working copy  (@) now at: mrxqplyk 1c72cd50 (conflict) ABCD
Parent commit (@-)      : kwtuwqnm 70985eaa ABC
Added 0 files, modified 1 files, removed 0 files
Warning: There are unresolved conflicts at these paths:
file    2-sided conflict
New conflicts appeared in 1 commits:
  mrxqplyk 1c72cd50 (conflict) ABCD
Hint: To resolve the conflicts, start by updating to it:
  jj new mrxqplyk
Then use `jj resolve`, or edit the conflict markers in the file directly.
Once the conflicts are resolved, you may want to inspect the result with `jj diff`.
Then run `jj squash` to move the resolution into the conflicted commit.
```

In the diff editor, use the arrow keys and spacebar to select all lines but the
last. Press 'c' to save the changes and close it. You can now inspect the
rewritten commit with `jj diff -r @-` again, and you should see your deletion of
the last line. Unlike `jj squash -i`, which left the content state of the commit
unchanged, `jj diffedit` (typically) results in a different state, which means
that descendant commits may have conflicts.

Another command for rewriting contents of existing commits is `jj split`. Now
that you've seen how `jj squash -i` and `jj diffedit` work, you can hopefully
figure out how it works (with the help of the instructions in the diff).