Using Git Worktrees

---
name: using-git-worktrees
description: Use when starting feature work that needs isolation from current workspace or before executing implementation plans - creates isolated git worktrees with smart directory selection and safety verification
---

# 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

```bash
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 / AGENTS.md

```bash
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 config preference:

```
No worktree directory found. Where should I create worktrees?

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

Which would you prefer?
```

## Safety Verification

### For Project-Local Directories

**MUST verify directory is ignored before creating worktree:**

```bash
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

**Why critical:** Prevents accidentally committing worktree contents to repository.

## Creation Steps

### 1. Detect Project Name

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

### 2. Create Worktree

```bash
git worktree add "$path" -b "$BRANCH_NAME"
cd "$path"
```

### 3. Run Project Setup

Auto-detect and run appropriate setup:

```bash
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 go.mod ]; then go mod download; fi
```

### 4. Verify Clean Baseline

```bash
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>
```

## Quick Reference

| Situation | Action |
|-----------|--------|
| `.worktrees/` exists | Use it (verify ignored) |
| `worktrees/` exists | Use it (verify ignored) |
| Both exist | Use `.worktrees/` |
| Neither exists | Check config → Ask user |
| Directory not ignored | Add to .gitignore + commit |
| Tests fail during baseline | Report failures + ask |

## Common Mistakes

**Skipping ignore verification** — worktree contents get tracked, pollute git status

**Assuming directory location** — violates project conventions

**Proceeding with failing tests** — can't distinguish new bugs from pre-existing issues

## Red Flags

**Never:**
- Create worktree without verifying it's ignored (project-local)
- Skip baseline test verification
- Proceed with failing tests without asking
- Assume directory location when ambiguous

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