jj/docs/github.md

Using Jujutsu with GitHub and GitLab Projects

This guide assumes a basic understanding of either Git or Mercurial.

Set up an SSH key

As of December 2022 it's recommended to set up an SSH key to work with GitHub projects. See GitHub's Tutorial. This restriction may be lifted in the future, see issue #469 for more information and progress on authenticated http.

Basic workflow

The simplest way to start with Jujutsu is to create a stack of commits first. You will only need to create a branch when you need to push the stack to a remote. There are two primary workflows, using a generated branch name or naming a branch.

Using a generated branch name

In this example we're letting Jujutsu auto-create a branch.

# Start a new commit off of the default branch.
$ jj new main
# Refactor some files, then add a description and start a new commit
$ jj commit -m 'refactor(foo): restructure foo()'
# Add a feature, then add a description and start a new commit
$ jj commit -m 'feat(bar): add support for bar'
# Let Jujutsu generate a branch name and push that to GitHub
$ jj git push -c @-

Using a named branch

In this example, we create a branch named bar and then push it to the remote.

# Start a new commit off of the default branch.
$ jj new main
# Refactor some files, then add a description and start a new commit
$ jj commit -m 'refactor(foo): restructure foo()'
# Add a feature, then add a description and start a new commit
$ jj commit -m 'feat(bar): add support for bar'
# Create a branch so we can push it to GitHub
$ jj branch create bar -r @- # create a branch `bar` that now contains the previous two commits.
# Push the branch to GitHub (pushes only `bar`)
$ jj git push

While it's possible to create a branch and commit on top of it in a Git-like manner, you will then need to move the branch manually when you create a new commits. Unlike Git, Jujutsu will not do it automatically .

Updating the repository.

As of December 2022, Jujutsu has no equivalent to a git pull command. Until such a command is added, you need to use jj git fetch followed by a jj rebase -d $main_branch to update your changes.

Working in a Git co-located repository

After doing jj init --git-repo=., git will be in a detached HEAD state, which is unusual, as git mainly works with branches. In a co-located repository, jj isn't the source of truth. But Jujutsu allows an incremental migration, as jj commit updates the HEAD of the git repository.

$ nvim docs/tutorial.md
$ # Do some more work.
$ jj commit -m "Update tutorial"
$ jj branch create doc-update
$ # Move the previous revision to doc-update.
$ jj branch set doc-update -r @-
$ jj git push

Working in a Jujutsu repository

In a Jujutsu repository, the workflow is simplified. If there's no need for explicitly named branches, you just can generate one for a change. As Jujutsu is able to create a branch for a revision.

$ # Do your work
$ jj commit
$ # Push change "mw", letting Jujutsu automatically create a branch called "push-mwmpwkwknuz"
$ jj git push --change mw 

Addressing review comments

There are two workflows for addressing review comments, depending on your project's preference. Many projects prefer that you address comments by adding commits to your branch¹. Some projects (such as Jujutsu and LLVM) instead prefer that you keep your commits clean by rewriting them and then force-pushing².

Adding new commits

If your project prefers that you address review comments by adding commits on top, you can do that by doing something like this:

$ # Create a new commit on top of the `your-feature` branch from above.
$ jj new your-feature
$ # Address the comments, by updating the code
$ jj diff
$ # Give the fix a description and create a new working-copy on top.
$ jj commit -m 'address pr comments'
$ # Update the branch to point to the new commit.
$ jj branch set your-feature -r @-
$ # Push it to your remote
$ jj git push

Notably, the above workflow creates a new commit for you. The same can be achieved without creating a new commit.

Warning

We strongly suggest to jj new after the example below, as all further edits still get amended to the previous commit.

$ # Create a new commit on top of the `your-feature` branch from above.
$ jj new your-feature
$ # Address the comments, by updating the code
$ jj diff
$ # Give the fix a description.
$ jj describe -m 'address pr comments'
$ # Update the branch to point to the current commit.
$ jj branch set your-feature -r @
$ # Push it to your remote
$ jj git push

Rewriting commits

If your project prefers that you keep commits clean, you can do that by doing something like this:

$ # Create a new commit on top of the second-to-last commit in `your-feature`,
$ # as reviews requested a fix there.
$ jj new your-feature- # NOTE: the trailing hyphen is not a typo!
$ # Address the comments by updating the code
$ # Review the changes
$ jj diff
$ # Squash the changes into the parent commit
$ jj squash
$ # Push the updated branch to the remote. Jujutsu automatically makes it a force push
$ jj git push --branch your-feature

The hyphen after your-feature comes from revset syntax.

Working with other people's branches

By default jj git clone and jj git fetch clone all active branches from the remote. This means that if you want to iterate or test another contributor's branch you can jj new <branchname> onto it.

If your remote has a large amount of old, inactive branches or this feature is undesirable, set git.auto-local-branch = false in the config file.

You can find more information on that setting here.

Using GitHub CLI

GitHub CLI will have trouble finding the proper git repository path in jj repos that aren't co-located (see issue #1008). You can configure the $GIT_DIR environment variable to point it to the right path:

$ GIT_DIR=.jj/repo/store/git gh issue list

You can make that automatic by installing direnv and defining hooks in a .envrc file in the repository root to configure $GIT_DIR. Just add this line into .envrc:

export GIT_DIR=$PWD/.jj/repo/store/git

and run direnv allow to approve it for direnv to run. Then GitHub CLI will work automatically even in repos that aren't co-located so you can execute commands like gh issue list normally.

Useful Revsets

Log all revisions across all local branches, which aren't on the main branch nor on any remote jj log -r 'branches() & ~(main | remote_branches())' Log all revisions which you authored, across all branches which aren't on any remote jj log -r 'mine() & branches() & ~remote_branches()' Log all remote branches, which you authored or committed to jj log -r 'remote_branches() & (mine() | committer(your@email.com))' Log all descendants of the current working copy, which aren't on a remote jj log -r '::@ & ~remote_branches()'

Merge conflicts

For a detailed overview, how Jujutsu handles conflicts, revisit the tutorial.

Using several remotes

It is common to use several remotes when contributing to a shared repository. For example, "upstream" can designate the remote where the changes will be merged through a pull-request while "origin" is your private fork of the project. In this case, you might want to jj git fetch from "upstream" and to jj git push to "origin".

You can configure the default remotes to fetch from and push to in your configuration file (for example .jj/repo/config.toml):

[git]
fetch = "upstream"
push = "origin"

The default for both git.fetch and git.push is "origin".

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1. This is a GitHub Style review, as GitHub currently only is able to compare branches. ↩︎

2. If you're wondering why we prefer clean commits in this project, see e.g. this blog post ↩︎