Using Git Worktrees

Announce: "Using git-worktrees skill for isolated workspace."

Invariant Principles

1. Directory precedence: existing > CLAUDE.md > ask user (never assume)
2. Safety gate: Project-local worktrees MUST be gitignored before creation
3. Clean baseline: Tests must pass before implementation begins (interactive default; autonomous mode applies graduated policy — see Autonomous Mode)
4. Auto-detect over hardcode: Infer setup from manifest files

Inputs

Outputs

Directory Selection Process

Follow this priority order:

1. Check Existing Directories

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 CLAUDE.md

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

If preference specified: Use it without asking.

3. Ask User

If no directory exists and no CLAUDE.md preference:

No worktree directory found. Where should I create worktrees?

1. .worktrees/ (project-local, hidden)
2. ~/.local/spellbook/worktrees/<project-name>/ (global location)

Which would you prefer?

Safety Verification

For Project-Local Directories (.worktrees or worktrees)

MUST verify directory is ignored before creating worktree:

git check-ignore -q .worktrees 2>/dev/null || git check-ignore -q worktrees 2>/dev/null

If NOT ignored:

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

For Global Directory (~/.local/spellbook/worktrees)

No .gitignore verification needed — outside project entirely.

Creation Steps

1. Detect Project Name

project=$(basename "$(git rev-parse --show-toplevel)")

2. Create Worktree

# Determine full path
case $LOCATION in
  .worktrees|worktrees)
    path="$LOCATION/$BRANCH_NAME"
    ;;
  ~/.local/spellbook/worktrees/*)
    path="~/.local/spellbook/worktrees/$project/$BRANCH_NAME"
    ;;
esac

# Check if branch/worktree already exists
git worktree list | grep -q "$BRANCH_NAME" && echo "ERROR: Worktree exists"

# Create worktree with new branch
git worktree add "$path" -b "$BRANCH_NAME"
cd "$path"

3. Run Project Setup

Auto-detect and run appropriate setup:

if [ -f package.json ]; then npm install; fi
if [ -f Cargo.toml ]; then cargo build; fi
if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
if [ -f pyproject.toml ]; then poetry install || uv sync; fi
if [ -f go.mod ]; then go mod download; fi

If setup fails: Report specific failure. Ask whether to proceed or troubleshoot.

4. Verify Clean Baseline

Run tests to ensure worktree starts clean:

# Use project-appropriate command: 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 <full-path>
Tests passing (<N> tests, 0 failures)
Ready to implement <feature-name>

Autonomous Mode Behavior

Check context for autonomous mode indicators:

• "Mode: AUTONOMOUS" or "autonomous mode"
• worktree preference specified (e.g., "single", "per_parallel_track", "none")

When autonomous mode is active:

Skip These Interactions

• "Where should I create worktrees?" — use default (.worktrees/) or CLAUDE.md preference
• "Tests fail during baseline — ask whether to proceed" — proceed if minor, pause if critical

Make These Decisions Autonomously

• Directory location: Use .worktrees/ as default if no existing directory or CLAUDE.md preference
• Gitignore fix: Always fix automatically (add to .gitignore + commit)
• Minor test failures: Log and proceed; major failures pause

Circuit Breakers (Always Pause For)

• All tests failing (baseline completely broken)
• Git worktree command fails (structural git issue)
• .gitignore cannot be modified (permissions or other issue)

Quick Reference

Common Mistakes

Example Workflow

[Check .worktrees/ - exists]
[Verify ignored - git check-ignore confirms .worktrees/ is ignored]
[Create worktree: git worktree add .worktrees/auth -b feature/auth]
[Run npm install]
[Run npm test - 47 passing]

Worktree ready at /Users/jesse/myproject/.worktrees/auth
Tests passing (47 tests, 0 failures)
Ready to implement auth feature

Before reporting worktree ready — if ANY unchecked, STOP and resolve:

• Directory location follows precedence (existing > CLAUDE.md > asked)
• Project-local path verified gitignored (or global path used)
• git worktree add completed successfully
• Dependencies installed for project type
• Baseline tests pass in new worktree </CRITICAL>

Integration

Called by:

• brainstorming (Phase 4) — REQUIRED when design is approved and implementation follows
• Any skill needing isolated workspace

Pairs with:

• finishing-a-development-branch — REQUIRED for cleanup after work complete
• executing-plans — Work happens in this worktree (supports both batch and subagent modes)

<FINAL_EMPHASIS> Worktree isolation protects the main workspace from experimental damage. Skipping safety verification causes repository pollution requiring manual cleanup. Proceeding without baseline tests makes it impossible to distinguish new bugs from pre-existing failures. Take the time to do it right. </FINAL_EMPHASIS>