feat: enhance environment file management with gitignore-based discovery

[aryasaatvik]

Summary

This PR significantly enhances agentree's environment file management by implementing intelligent discovery based on .gitignore patterns. This addresses the need for better environment configuration support, especially for monorepos and AI tool configurations.

Key Improvements

• 🔍 Gitignore-based Discovery: Uses .gitignore patterns as the source of truth for finding environment files
• 📁 Monorepo Support: Recursively discovers nested environment files (e.g., packages/*/.env)
• 🤖 AI Tool Configurations: Automatically copies .claude/settings.local.json, .cursorrules, and other AI configs
• ⚙️ Flexible Configuration: New options in .agentreerc and global config for customizing behavior
• 🎯 Include/Exclude Patterns: Add custom patterns or exclude unwanted files
• ✅ Comprehensive Tests: Full test coverage for all new features
• 📚 Documentation: Detailed guide for environment configuration

How It Works

1. Parses all .gitignore files in the repository
2. Identifies patterns that likely represent environment/configuration files
3. Finds actual files matching those patterns
4. Adds default AI tool configuration patterns
5. Applies custom include/exclude patterns from configuration
6. Copies all discovered files to the new worktree, preserving directory structure

Configuration Example

# .agentreerc
ENV_COPY_ENABLED=true
ENV_RECURSIVE=true
ENV_USE_GITIGNORE=true

ENV_INCLUDE_PATTERNS=(
  "*.env.example"
  "config/*.sample"
  ".vscode/settings.local.json"
)

ENV_EXCLUDE_PATTERNS=(
  "*.test.env"
  "node_modules/**/.env"
)

Testing

All tests pass with comprehensive coverage:

• ✅ Gitignore parsing and pattern matching
• ✅ Environment file discovery
• ✅ Monorepo recursive search
• ✅ Configuration loading and merging
• ✅ File copying with directory preservation

Breaking Changes

None - the implementation maintains backward compatibility. If gitignore parsing fails or no files are discovered, it falls back to the legacy behavior of copying only .env and .dev.vars.

🤖 Generated with Claude Code