Implement automated monthly branch cleanup policy and announcement system

[Copilot]

Overview

This PR implements a comprehensive automated branch cleanup system to maintain repository health, security, and performance by removing branches older than 24 months on a monthly basis.

Background

Based on recent analysis, the repository contains approximately 1,436 branches older than 24 months (as identified in GitHub Action logs). This cleanup policy addresses:

• Repository Health: Reduces repository size and improves Git operation performance
• Security: Removes old branches that may contain outdated dependencies or vulnerabilities
• Maintainability: Simplifies branch management for contributors and maintainers
• Best Practices: Aligns with industry standards for repository hygiene

Implementation Details

🎯 Issue Template for Announcements

• File: .github/ISSUE_TEMPLATE/branch_cleanup_announcement.yml
• Pre-filled announcement template referencing the cleanup policy
• Includes timeline, exclusion request process, and policy details
• Ready for immediate use to announce the policy to the community

🤖 Automated Cleanup Workflow

• File: .github/workflows/branch-cleanup.yml
• Schedule: Runs automatically on the first Monday of each month at 2:00 AM UTC
• Manual Trigger: Can be executed on-demand with configurable parameters
• Safety Features:
  • Dry-run mode for testing without actual deletion
  • Protected branch patterns that are never deleted
  • Comprehensive error handling and logging
  • Automatic cleanup report generation via GitHub issues

🛡️ Protected Branch Patterns

The following branches are permanently protected from cleanup:

• master and main - Main development branches
• release* - All release branches (e.g., releases/m158)
• Localize* and Localization* - Localization branches

📚 Documentation

• Policy Document: docs/branch-cleanup-policy.md - Complete governance and procedures
• Implementation Guide: docs/branch-cleanup-README.md - Step-by-step usage instructions
• Summary: BRANCH_CLEANUP_SUMMARY.md - Quick action items for maintainers

🔄 Workflow Migration

• Updated existing branch-cleanup-preview.yml with deprecation notice
• New workflow provides both preview and production capabilities
• Maintains backward compatibility

Key Features

✅ Automated Monthly Execution - No manual intervention required
✅ Safe Testing - Dry-run mode prevents accidental deletions
✅ Smart Protection - Pattern-based protection for critical branches
✅ Comprehensive Reporting - Automatic GitHub issue creation with cleanup details
✅ Flexible Configuration - Adjustable retention periods and options
✅ Error Recovery - Graceful handling of protected or missing branches

Usage

For Repository Maintainers

1. Create announcement issue using the provided template
2. Test the workflow in dry-run mode
3. Set appropriate grace period (recommended: 30 days)
4. Enable automatic monthly execution

For Contributors

• Keep active branches current
• Merge completed work via pull requests
• Maintain local copies of important branches
• Use Git tags for important milestones

Security & Compliance

• Vulnerability Reduction: Removes branches with potentially outdated dependencies
• Audit Trail: Complete logging and reporting of all cleanup operations
• Controlled Access: Requires appropriate repository permissions
• Rollback Safety: Branch recovery possible immediately after deletion

Testing

All YAML files have been validated for syntax correctness. The workflow includes:

• Comprehensive error handling for edge cases
• Protection against deleting important branches
• Detailed logging for troubleshooting and auditing
• Safe defaults that require explicit confirmation for destructive operations

This implementation provides a production-ready solution that balances automation efficiency with safety and transparency.

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