using-git-worktrees

name	using-git-worktrees
description	Create isolated git worktrees with E2E port isolation for parallel development
disable-model-invocation	true

Using Git Worktrees with E2E Port Isolation

Overview

Git worktrees allow you to have multiple working directories for the same repository, enabling true parallel development without branch switching. This skill covers creating worktrees with proper E2E test port isolation.

Creating a Worktree

# 1. Create the worktree
git worktree add ../wt-<ISSUE>-<description> -b <branch-name>

# 2. Navigate to worktree
cd ../wt-<ISSUE>-<description>

# 3. Set up E2E port isolation (MANDATORY)
./scripts/setup-worktree-e2e.sh

# 4. Verify setup
cat .env.e2e  # Shows your isolated ports

Example

# Create worktree for DBB-330
git worktree add ../wt-DBB-330-login-form -b feat/DBB-330-login-form
cd ../wt-DBB-330-login-form

# Set up port isolation
./scripts/setup-worktree-e2e.sh

# Verify
cat .env.e2e
# Output:
# E2E_PORT_BASE=3573
# BINGO_PORT=3573
# TRIVIA_PORT=3574
# HUB_PORT=3575

Starting Dev Servers

Option A: Use Helper Script (Recommended)

./start-e2e-servers.sh

This script:

• Sources .env.e2e automatically
• Starts all three dev servers on isolated ports
• Runs servers in background with proper process management

Option B: Manual (with Port Awareness)

# Load port configuration
source .env.e2e

# Start each server on its isolated port
PORT=$BINGO_PORT pnpm --filter @double-bind/desktop dev &
PORT=$TRIVIA_PORT pnpm --filter @double-bind/core dev &
PORT=$HUB_PORT pnpm --filter @double-bind/cli dev &

Running E2E Tests

After servers are running, E2E tests automatically use the correct ports:

# Playwright auto-detects worktree and uses ports from .env.e2e
pnpm test:e2e

# Run specific test file
pnpm test:e2e e2e/bingo/home.spec.ts

Port Allocation

The port allocation system uses a deterministic hash of the worktree path:

Main repo:     ports 3000, 3001, 3002
Worktree 1:    ports 3XXX, 3XXX, 3XXX (based on path hash)
Worktree 2:    ports 3YYY, 3YYY, 3YYY (different hash)
Worktree 3:    ports 3ZZZ, 3ZZZ, 3ZZZ (different hash)

Range: 3000-3999 (supports up to 333 concurrent worktrees)

Why Port Isolation Matters

Without Port Isolation ❌

# Main repo running on 3000-3002
pnpm dev

# Worktree tries to use same ports
cd ../wt-DBB-330-login-form
pnpm dev  # ❌ EADDRINUSE: address already in use :::3000

Result: Port conflicts, servers fail to start, E2E tests cannot run.

With Port Isolation ✅

# Main repo on 3000-3002
pnpm dev

# Worktree uses isolated ports (e.g., 3573-3575)
cd ../wt-DBB-330-login-form
./scripts/setup-worktree-e2e.sh
./start-e2e-servers.sh  # ✅ Servers start on 3573-3575

Result: True parallel development - main repo and multiple worktrees run simultaneously.

Cleanup

When done with a worktree:

# Stop servers (if running in background)
pkill -f "next-server.*3573"  # Replace 3573 with your base port

# Remove worktree
cd /path/to/main/repo
git worktree remove ../wt-DBB-330-login-form

Troubleshooting

"Missing .env.e2e file"

Problem: Forgot to run setup script after creating worktree.

Fix:

./scripts/setup-worktree-e2e.sh

"Port already in use"

Problem: Another worktree or process is using the calculated port.

Fix:

# Override with specific port
E2E_PORT_BASE=3999 ./scripts/setup-worktree-e2e.sh

# Verify new ports
cat .env.e2e

"Playwright uses wrong ports"

Problem: .env.e2e exists but Playwright config not loading it.

Fix:

# Verify portConfig is exported in playwright.config.ts
grep -A 10 "export const portConfig" playwright.config.ts

# Verify worktree detection
pnpm test:e2e --list  # Should show detected worktree in URL

Reference

• Setup Script: scripts/setup-worktree-e2e.sh
• Port Isolation Module: e2e/utils/port-isolation.ts
• Playwright Config: playwright.config.ts (exports portConfig)
• Full Documentation: docs/E2E_TESTING_GUIDE.md section "Parallel Task Execution with Port Isolation"

Best Practices

1. Always run setup script immediately after creating worktree
2. Use ./start-e2e-servers.sh for consistent server startup
3. Verify .env.e2e exists before running E2E tests
4. Clean up worktrees when done to free resources
5. Don't commit .env.e2e to version control (already in .gitignore)

Integration with Subagent Workflow

When using the subagent workflow:

• Step 2: Create worktree + run setup script (both required)
• Step 3: Implementer agents use ./start-e2e-servers.sh to start servers
• Step 4-5: Reviewers verify .env.e2e exists and servers run on isolated ports
• Step 6: Cleanup worktree after PR merged

This ensures true parallel execution across multiple Linear issues without port conflicts.