jj/docs/working-copy.md

Working copy

Introduction

The working copy is where the current working-copy commit's files are written so you can interact with them. It also where files are read from in order to create new commits (though there are many other ways of creating new commits).

Unlike most other VCSs, Jujutsu will automatically create commits from the working-copy contents when they have changed. Most jj commands you run will commit the working-copy changes if they have changed. The resulting revision will replace the previous working-copy revision.

Also unlike most other VCSs, added files are implicitly tracked. That means that if you add a new file to the working copy, it will be automatically committed once you run e.g. jj st. Similarly, if you remove a file from the working copy, it will implicitly be untracked. To untrack a file while keeping it in the working copy, first make sure it's ignored and then run jj untrack <path>.

Conflicts

When you check out a commit with conflicts, those conflicts need to be represented in the working copy somehow. However, the file system doesn't understand conflicts. Jujutsu's solution is to add conflict markers to conflicted files when it writes them to the working copy. It also keeps track of the (typically 3) different parts involved in the conflict. Whenever it scans the working copy thereafter, it parses the conflict markers and recreates the conflict state from them. You can resolve conflicts by replacing the conflict markers by the resolved text. You don't need to resolve all conflicts at once. You can even resolve part of a conflict by updating the different parts of the conflict marker.

To resolve conflicts in a commit, use jj new <commit> to create a working-copy commit on top. You would then have the same conflicts in the working-copy commit. Once you have resolved the conflicts, you can inspect the conflict resolutions with jj diff. Then run jj squash to move the conflict resolutions into the conflicted commit. Alternatively, you can edit the commit with conflicts directly in the working copy by using jj edit <commit>. The main disadvantage of that is that it's harder to inspect the conflict resolutions.

With the jj resolve command, you can use an external merge tool to resolve conflicts that have 2 sides and a base. There is not yet a good way of resolving conflicts between directories, files, and symlinks (https://github.com/martinvonz/jj/issues/19). You can use jj restore to choose one side of the conflict, but there's no way to even see where the involved parts came from.

Ignored files

You probably don't want build outputs and temporary files to be under version control. You can tell Jujutsu to not automatically track certain files by using .gitignore files (there's no such thing as .jjignore yet). See https://git-scm.com/docs/gitignore for details about the format. .gitignore files are supported in any directory in the working copy, as well as in $HOME/.gitignore and $GIT_DIR/info/exclude.

Workspaces

You can have multiple working copies backed by a single repo. Use jj workspace add to create a new working copy. The working copy will have a .jj/ directory linked to the main repo. The working copy and the .jj/ directory together is called a "workspace". Each workspace can have a different commit checked out.

Having multiple workspaces can be useful for running long-running tests in a one while you continue developing in another, for example. If needed, jj workspace root prints the root path of the current workspace.

When you're done using a workspace, use jj workspace forget to make the repo forget about it. The files can be deleted from disk separately (either before or after).

Stale working copy

When you modify workspace A's working-copy commit from workspace B, workspace A's working copy will become stale. By "stale", we mean that the files in the working copy don't match the desired commit indicated by the @ symbol in jj log. When that happens, use jj workspace update-stale to update the files in the working copy.