bacchus-labs/using-git-worktrees

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.

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 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. ~/.config/wrangler/worktrees/<project-name>/ (global location)

Which would you prefer?

Safety Verification

For Project-Local Directories (.worktrees or worktrees)

MUST verify .gitignore before creating worktree:

# Check if directory pattern in .gitignore
grep -q "^\.worktrees/$" .gitignore || grep -q "^worktrees/$" .gitignore

If NOT in .gitignore:

Per our rule "Fix broken things immediately":

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

Why critical: Prevents accidentally committing worktree contents to repository.

For Global Directory (~/.config/wrangler/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/$BRANCH_NAME"
    ;;
  ~/.config/wrangler/worktrees/*)
    path="~/.config/wrangler/worktrees/$project/$BRANCH_NAME"
    ;;
esac

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

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:

# Examples - 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. Store Absolute Path

CRITICAL: Capture and store the absolute path for subagent use:

# Store absolute path (resolves any symlinks)
WORKTREE_ABSOLUTE="$(cd "$path" && pwd -P)"
WORKTREE_BRANCH="$BRANCH_NAME"

echo "WORKTREE_ABSOLUTE=$WORKTREE_ABSOLUTE"
echo "WORKTREE_BRANCH=$WORKTREE_BRANCH"

These values MUST be passed to all subagents working in this worktree.

6. Report Location

Worktree ready at: $WORKTREE_ABSOLUTE
Branch: $WORKTREE_BRANCH
Tests passing (<N> tests, 0 failures)

IMPORTANT: For all work in this worktree, use this command pattern:
  cd $WORKTREE_ABSOLUTE && [command]

Ready to implementing-issue <feature-name>

Quick Reference

| Situation | Action | | --------------------------- | --------------------------- | | .worktrees/ exists | Use it (verify .gitignore) | | worktrees/ exists | Use it (verify .gitignore) | | Both exist | Use .worktrees/ | | Neither exists | Check CLAUDE.md → Ask user | | Directory not in .gitignore | Add it immediately + commit | | Tests fail during baseline | Report failures + ask | | No package.json/Cargo.toml | Skip dependency install |

Common Mistakes

Skipping .gitignore verification

• Problem: Worktree contents get tracked, pollute git status
• Fix: Always grep .gitignore before creating project-local worktree

Assuming directory location

• Problem: Creates inconsistency, violates project conventions
• Fix: Follow priority: existing > CLAUDE.md > ask

Proceeding with failing tests

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

Hardcoding setup commands

• Problem: Breaks on projects using different tools
• Fix: Auto-detect from project files (package.json, etc.)

Example Workflow

You: I'm using the using-git-worktrees skill to set up an isolated workspace.

[Check .worktrees/ - exists]
[Verify .gitignore - contains .worktrees/]
[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 implementing-issue auth feature

Red Flags

Never:

• Create worktree without .gitignore verification (project-local)
• Skip baseline test verification
• Proceed with failing tests without asking
• Assume directory location when ambiguous
• Skip CLAUDE.md check

Always:

• Follow directory priority: existing > CLAUDE.md > ask
• Verify .gitignore for project-local
• Auto-detect and run project setup
• Verify clean test baseline

Worktree Isolation (CRITICAL)

Problem: Claude Code resets working directory between Bash calls. Subagents don't inherit your location context.

Solution: See isolating-worktrees skill for the full protocol. Key points:

1. Always chain commands: cd $WORKTREE && git status (not separate calls)
2. Pass absolute path to subagents: Include verification in every subagent prompt
3. Verify before git operations: Check you're in the right place before committing

Required subagent prompt pattern:

## Working Directory (CRITICAL)

Worktree: [WORKTREE_ABSOLUTE]
Branch: [WORKTREE_BRANCH]

### Verify First (MANDATORY)
```bash
cd [WORKTREE_ABSOLUTE] && \
  echo "Directory: $(pwd)" && \
  echo "Branch: $(git branch --show-current)" && \
  test "$(pwd)" = "[WORKTREE_ABSOLUTE]" && echo "VERIFIED" || echo "FAILED"

Command Pattern

ALL commands: cd [WORKTREE_ABSOLUTE] && [command]

## Integration

**Called by:**

- **brainstorming** (Phase 5) - Optional for isolation when design is approved and implementation follows
- **implementing-issue** - When user wants isolated workspace for implementation
- Any skill needing isolated workspace

**Pairs with:**

- **isolating-worktrees** - MUST use when dispatching subagents to work in worktree
- **finishing-a-development-branch** - Optional cleanup after work complete (handles both worktree and non-worktree cases)
- **implementing-issue** - Work happens in worktree with isolation protocol