Using Git Worktrees

Overview

Git worktrees create isolated workspaces sharing the same repository, allowing work on multiple branches simultaneously without switching.

Core principle: Systematic directory selection + safety verification = reliable isolation.

Announce at start: "I'm using the git-worktree skill to set up an isolated workspace."

When to Use

• Before executing implementation plans (/superspec:execute)
• When starting a new change that needs isolation
• When you need to work on multiple changes simultaneously

Directory Selection Process

Follow this priority order:

1. Check Existing Directories

# Check in priority order
ls -d .worktrees 2>/dev/null     # Preferred (hidden)
ls -d worktrees 2>/dev/null      # Alternative

If found: Use that directory. If both exist, .worktrees wins.

2. Check Project Configuration

grep -i "worktree.*director" CLAUDE.md 2>/dev/null
grep -i "worktree.*director" superspec/project.md 2>/dev/null

If preference specified: Use it without asking.

3. Ask User

If no directory exists and no preference:

No worktree directory found. Where should I create worktrees?

1. .worktrees/ (project-local, hidden) - Recommended
2. worktrees/ (project-local, visible)

Which would you prefer?

Safety Verification

For Project-Local Directories

MUST verify directory is ignored before creating worktree:

# Check if directory is ignored
git check-ignore -q .worktrees 2>/dev/null || git check-ignore -q worktrees 2>/dev/null

If NOT ignored:

1. Add to .gitignore
2. Commit the change
3. Proceed with worktree creation

Why critical: Prevents accidentally committing worktree contents to repository.

Creation Steps

1. Determine Change ID

Use the change ID from SuperSpec:

change_id="add-2fa"  # From superspec/changes/[change-id]/

2. Create Worktree

# Create worktree with new branch
git worktree add .worktrees/$change_id -b feature/$change_id

# Navigate to worktree
cd .worktrees/$change_id

3. Run Project Setup

Auto-detect and run appropriate setup:

# Node.js
if [ -f package.json ]; then npm install; fi

# Rust
if [ -f Cargo.toml ]; then cargo build; fi

# Python
if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
if [ -f pyproject.toml ]; then poetry install; fi

# Go
if [ -f go.mod ]; then go mod download; fi

4. Verify Clean Baseline

Run tests to ensure worktree starts clean:

npm test / cargo test / pytest / go test ./...

If tests fail: Report failures, ask whether to proceed or investigate.

If tests pass: Report ready.

5. Report Location

Worktree ready at .worktrees/[change-id]
Branch: feature/[change-id]
Tests: Passing (N tests, 0 failures)

SuperSpec documents:
- Proposal: superspec/changes/[change-id]/proposal.md
- Design: superspec/changes/[change-id]/design.md
- Specs: superspec/changes/[change-id]/specs/

Ready to implement. Next: /superspec:execute

Quick Reference

Common Mistakes

Skipping ignore verification

• Problem: Worktree contents get tracked, pollute git status
• Fix: Always use git check-ignore before creating project-local worktree

Proceeding with failing tests

• Problem: Can't distinguish new bugs from pre-existing issues
• Fix: Report failures, get explicit permission to proceed

Red Flags

Never:

• Create worktree without verifying it's ignored (project-local)
• Skip baseline test verification
• Proceed with failing tests without asking

Always:

• Follow directory priority: existing > config > ask
• Verify directory is ignored for project-local
• Auto-detect and run project setup
• Verify clean test baseline

Integration

Called by:

• plan-writing - After plan creation, before execution

Pairs with:

• finish-branch - Cleans up worktree after work complete
• subagent-development - Work happens in this worktree