Working with Git

Your jj repository can push and pull Git branches, and jj has additional functionality for working with Git. Try jj git --help to see a list of subcommands.

First steps

For learning purposes, you could clone this tutorial's Git repository to look around:

$ jj git clone https://github.com/evmar/jjtut.git
$ jj log
@  kpmzwpnw my@email fc5fe481
│  (empty) (no description set)
◆  mzrrnrom evan.martin@gmail.com main@origin ead50b5a
│  broken link
~

Here are some things to notice:

1. The commit log ends with a ~ to show it was truncated.
2. The commit mzrrnrom is from the upstream repository. It is marked with a diamond to show it is immutable, a new jj concept.
3. The commit is tagged with main@origin.

We'll go into these in order.

Truncated log

The jj log command by default will attempt to omit some commits, including commits from remote repositories. This is configurable, but for now if you'd like to see all commits you can use:

$ jj log -r ::

The :: is the jj revset expression for "all commits".

Immutable commits

If you attempt to edit the immutable commit, jj will refuse:

$ jj edit mzrrnrom
Error: Commit ead50b5a160a is immutable
Hint: Could not modify commit: mzrrnrom main@origin | broken link
Hint: Immutable commits are used to protect shared history.
Hint: For more information, see:
      - https://docs.jj-vcs.dev/latest/config/#set-of-immutable-commits
      - `jj help -k config`, "Set of immutable commits"
Hint: This operation would rewrite 1 immutable commits.

jj considers commits from remote branches immutable so you don't accidentally edit them.

This immutability is more of a guardrail than a strict law. You can not only reconfigure which commits are consided immutable, you can also often pass --ignore-immutable to commands that complain in cases where you know better. It's there to help prevent accidents.

But it's probably not a good idea to bypass the immutability here, because editing this commit is likely to make things conflict if you attempt to sync with upstream again.

Bookmarks

Finally, the main@origin bit in the log on the upstream commit is a jj bookmark, a jj feature seen here for the first time.

A jj bookmark is a name attached to a commit, similar to a Git tag. Here, the bookmark named main@origin points at the current main branch in the upstream repository. We'll go into them next.

Review

• commits coming from Git remotes are immutable and not shown in the default log
• attempting to edit an immutable commit is an error
• Git branches show up as jj bookmarks

Next step

To push Git changes we need to learn about bookmarks.