Jujutsu Version Control

Jujutsu Version Control Skill

This skill ensures Claude uses jujutsu (jj) as the primary version control system for all VCS operations in this repository.

Core Principle

Prefer jj for all VCS actions; translate git requests to jj.

When users reference version control operations using git terminology, automatically translate them to jujutsu equivalents. Only fall back to git if jujutsu is unavailable and the user explicitly approves.

AI Transparency

When Claude creates commits in this repository:

Commit Attribution: Every AI-generated commit should include @claude in the commit title for immediate transparency.

• Format: Add feature X @claude or Fix bug in Y @claude
• You can omit ", thanks" if it flows better - just @claude is sufficient
• This makes it obvious which commits involved AI assistance

Examples:

• Good: Add jujutsu skill documentation @claude
• Good: Fix timeout handling @claude
• Also good: Refactor service.py @claude

When This Skill Activates

This skill activates when users mention:

• VCS actions: commit, branch, merge, rebase, push, pull, checkout, stash
• Repository state: staged, unstaged, HEAD, detached, conflicts
• Jujutsu-specific terms: bookmarks, workspaces, revsets, operation log, working-copy commit

Keyword Tripwires: git, repo, commit, branch, merge, rebase, bookmark, workspace, revset, working-copy

Key Jujutsu Concepts

Working Copy as Commit

In jujutsu, the working copy is itself a commit:

• @ represents the working-copy commit (equivalent to git's "working directory + staging area")
• @- represents the parent of the working-copy commit
• Changes are automatically tracked in @ without explicit staging

Bookmarks (not Branches)

Jujutsu uses bookmarks instead of branches:

• Bookmarks are pointers to commits, managed with jj bookmark commands
• Critical: Bookmarks do NOT auto-advance when you create new commits
• You must explicitly move bookmarks: jj bookmark set <name>
• Bookmarks are local by default; use --track for remote tracking

Workspaces

Workspaces allow multiple working copies of the same repository:

• Similar to git worktrees but more integrated
• Each workspace has its own working-copy commit
• Useful for parallel work on different features

Git Interoperability

Jujutsu can colocate with git repositories:

• jj git init creates a jj repo that tracks a git repo
• jj git clone clones a git repository with jj tracking
• In colocated repos, prefer jj for write operations
• jj git push and jj git fetch sync with git remotes

Common Command Translations

Status and Inspection

Creating and Editing Changes

Movement and History Editing

Bookmarks (Branches)

Undo Operations

Remote Operations

File Operations

Working Patterns

Creating a New Change

# Make changes to files
jj status                    # Review changes
jj commit -m "description"   # Create commit from working-copy
# Working-copy is now a new empty commit on top

Amending the Current Change

# Make more changes
jj describe -m "updated description"  # Update message
jj squash                             # Squash into parent (alternative)

Creating a Feature Bookmark

jj bookmark create feature-name    # Create bookmark at @
jj describe -m "feature: ..."      # Describe the change
jj commit -m "feature: part 2"     # Continue work
jj bookmark set feature-name       # Move bookmark to @ (if needed)

Splitting a Change

jj split                    # Interactively split current commit
# OR
jj split <file1> <file2>   # Split specific files into new commit

Viewing History

jj log                      # Visual graph of all commits
jj log -r ::@              # Ancestors of working-copy
jj log -r @-               # Parent commit
jj log -r 'bookmarks()'    # All bookmarked commits
jj log --summary           # Show commits with list of modified files

Reviewing Commit Changes

jj show                    # Show current commit (@) with description and full diff
jj show --git              # Same but in clearer git diff format (recommended)
jj show <revision>         # Show specific commit with changes
jj diff -r @               # Show changes in current commit (same as jj diff)
jj diff -r <revision>      # Show changes in specific revision

Important: jj diff by default shows changes IN the current commit @, NOT uncommitted working copy changes (since the working copy IS the commit @ in jujutsu).

Undoing Mistakes

jj op log                   # View operation history
jj undo                     # Undo last operation
jj op restore <op-id>      # Restore to specific operation

Recommended Pre-Edit Workflow

When making file changes, follow this pattern to keep AI and human changesets separate:

1. Check current working-copy status:

   jj status                # Check if @ has changes
   jj log -r @              # Check description and @claude tag
   

2. If @ has changes:

   Case A: Description contains @claude (previous AI work)

   # Commit previous AI work to keep changesets separate
   jj commit
   

   Case B: Description does NOT contain @claude (user work)

   # If no description set: auto-describe from diff
   jj diff                                    # Review changes
   jj describe -m "<description from diff>"  # Describe user's changes
   jj commit                                  # Commit user work
   
   # If description already exists: ASK user before proceeding
   # Don't auto-change existing descriptions - verify first
   

3. Make your new changes (Edit/Write files)

4. Format Nix files if modified:

   nixfmt **/*.nix         # Format all Nix files before committing
   

5. Describe and commit the new AI changes:

   jj describe -m "Your change description @claude"
   jj commit
   

Key Principles:

• The working-copy commit (@) is essentially jj's "staging area"
• Always separate AI and human commits using @claude tag
• Commit more often rather than less (Claude can't split commits interactively)
• If user's commit already has a description, ask before modifying it
• Humans manually squash/refine history later if needed

When to use: Recommended for all tasks involving file edits.

Best Practices for This Repository

1. Use @claude attribution in all AI-generated commit titles: Makes AI involvement immediately obvious in history
2. Format Nix files before committing: Run nixfmt **/*.nix before any commit to ensure consistent formatting
3. Check jj status before making edits: Handle existing changes cleanly by committing them first
4. Separate AI and human changesets: Never mix user work and AI work in the same commit
5. Create frequent commits: Jujutsu makes history editing easy, so commit often with reasonable changesets
6. Use descriptive commit messages: Follow the style from jj log output
7. Leverage operation log: jj op log is your safety net - you can always undo
8. Don't worry about "perfect" commits: History is mutable and easy to refine
9. Use jj bookmark set: Remember to move bookmarks when needed (they don't auto-advance)

Safety Notes

• Jujutsu does not have a "current branch": Bookmarks require explicit management
• Working-copy is always a commit: Changes are never lost unless explicitly abandoned
• Operations are recorded: jj op log tracks every action for easy undo
• Colocated repos: In repos with both jj and git, prefer jj for write operations
• Sacred bookmarks: Never automatically advance main, master, or trunk bookmarks - these are managed by humans only

Repository-Specific Conventions

Based on the nix-csi repository:

• Use descriptive commit messages (see examples in jj log)
• Recent commit message patterns:
  • "Add X to Y" for new features
  • "Make X configurable" for configuration changes
  • "Use X instead of Y" for refactoring
  • "Document X in Y" for documentation
• Commit frequently during development; history can be refined later

When Jujutsu Is Unavailable

If jj is not installed:

1. Inform the user that jujutsu is preferred for this repository
2. Suggest installation: cargo install jj-cli or system package manager
3. Only proceed with git commands if the user explicitly approves
4. Remind the user of the benefits of switching to jujutsu

References

• Jujutsu documentation: https://martinvonz.github.io/jj/
• GitHub repository: https://github.com/martinvonz/jj
• This repository's VCS policy: See CLAUDE.md

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