git-worktrees

# Git Worktrees

## Overview

Git worktrees create isolated workspaces sharing the same repository, allowing
work on multiple branches simultaneously without switching. Each worktree is a
separate directory with its own working tree, but they share the same `.git`
history.

## When to Use Worktrees

- **Parallel development**: Work on feature A while feature B builds/tests
- **Code review**: Check out PR branch without disrupting current work
- **Experiments**: Try something risky without affecting main workspace
- **Long-running tasks**: Keep main branch available while feature develops

## Quick Reference

| Action | Command |
|--------|---------|
| List worktrees | `git worktree list` |
| Create worktree | `git worktree add <path> -b <branch>` |
| Create from existing branch | `git worktree add <path> <branch>` |
| Remove worktree | `git worktree remove <path>` |
| Prune stale worktrees | `git worktree prune` |

## Creating Worktrees

### New Feature Branch

```bash
# Create worktree with new branch
git worktree add .worktrees/my-feature -b feat/my-feature

# Or specify base branch
git worktree add .worktrees/my-feature -b feat/my-feature main
```

### From Existing Branch

```bash
# Check out existing remote branch
git worktree add .worktrees/pr-review origin/fix-bug

# Check out existing local branch
git worktree add .worktrees/hotfix hotfix/urgent-fix
```

## Directory Structure

```
project/
├── .git/                    # Shared git history
├── .worktrees/              # Convention: keep worktrees here
│   ├── feature-a/           # First worktree
│   └── feature-b/           # Second worktree
└── src/                     # Main worktree files
```

## Setup After Creating Worktree

After creating a worktree, you typically need to:

```bash
cd .worktrees/my-feature

# Install dependencies
npm install  # or pnpm install, yarn, etc.

# Copy any required env files
cp ../.env .env.local

# Verify setup
npm test
```

## Safety Rules

**NEVER remove a worktree with uncommitted changes without confirmation.**

```bash
# Check for uncommitted changes first
git -C .worktrees/my-feature status --porcelain

# If empty, safe to remove
git worktree remove .worktrees/my-feature

# Delete the branch after merge (-d is safe, fails if not merged)
git branch -d feat/my-feature
```

### Removal Decision Matrix

| PR Merged? | Uncommitted Changes? | Action |
|------------|---------------------|--------|
| Yes | No | Safe to remove |
| Yes | Yes | Ask user - changes will be lost |
| No | No | Do NOT remove - work not preserved |
| No | Yes | Do NOT remove - active work |

## Cleaning Up Worktrees

### Manual Cleanup

```bash
# 1. Check if work is merged (if using GitHub)
gh pr list --head feat/my-feature --state merged

# 2. Check for uncommitted changes
git -C .worktrees/my-feature status --porcelain

# 3. Remove worktree (only if merged or confirmed with user)
git worktree remove .worktrees/my-feature

# 4. Delete branch
git branch -d feat/my-feature
```

### Prune Stale Worktrees

If a worktree directory was deleted manually:

```bash
git worktree prune
```

## Common Patterns

### Review a PR

```bash
# Create worktree from PR branch
git fetch origin pull/123/head:pr-123
git worktree add .worktrees/pr-123 pr-123

# Review, test, then clean up
git worktree remove .worktrees/pr-123
git branch -D pr-123
```

### Parallel Feature Development

```bash
# Main work continues in project root
# Start new feature in worktree
git worktree add .worktrees/new-api -b feat/new-api

# Work on both simultaneously
code .worktrees/new-api  # Opens new VS Code window
```

## Troubleshooting

### "Branch already checked out"

A branch can only be checked out in one worktree at a time:

```bash
# Find where branch is checked out
git worktree list

# Remove that worktree first, or use different branch
```

### "Worktree directory not empty"

```bash
# Force add if directory exists but isn't a worktree
git worktree add --force <path> <branch>
```

### Locked Worktree

If a worktree is locked (prevents accidental removal):

```bash
# Unlock it
git worktree unlock <path>

# Then remove
git worktree remove <path>
```