Summary

• Added --result-json-file option to output sync results as JSON
• Distinguish between create and update actions based on file reason
• Support for both dry-run and actual execution modes

Motivation

Closes #2

This feature enables CI/CD pipelines to programmatically determine which files have changed during sync operations. The JSON output can be used to:

• Trigger CloudFront cache invalidation for changed files only
• Generate deployment reports
• Make automated deployment decisions

Changes

1. New CLI option: --result-json-file <path>
2. JSON output structure:
   • changes: Array of file change details
   • summary: Statistics (created, updated, deleted, failed)
3. Action types: Properly distinguish between create and update based on the sync reason

JSON Output Format

Create/Update Operations

{
  "action": "create",
  "source": "/path/to/local/file.txt",
  "target": "s3://bucket/prefix/file.txt"
}

Delete Operations

{
  "action": "delete",
  "target": "s3://bucket/prefix/file.txt"
}

Complete Example

{
  "changes": [
    {
      "action": "create",
      "source": "/Users/yuya/project/file1.txt",
      "target": "s3://my-bucket/prefix/file1.txt"
    },
    {
      "action": "update",
      "source": "/Users/yuya/project/file2.txt",
      "target": "s3://my-bucket/prefix/file2.txt"
    },
    {
      "action": "delete",
      "target": "s3://my-bucket/prefix/old-file.txt"
    }
  ],
  "summary": {
    "total_files": 3,
    "created": 1,
    "updated": 1,
    "deleted": 1,
    "failed": 0
  }
}

Breaking Changes

⚠️ This PR includes breaking changes to the JSON output format:

1. Changed from from/to to source/target pattern
2. Delete operations now only have target field (no source)
3. Removed unused skip field from summary

This structure provides clearer semantics and enables future extensibility for S3-to-local and S3-to-S3 sync operations.

Test Plan

• Test dry-run mode with JSON output
• Test actual sync with JSON output
• Verify create vs update distinction
• Test with various sync scenarios (create, update, delete)
• Verify JSON file is created with proper permissions (0644)
• Test error handling and failed operations in JSON output

🤖 Generated with Claude Code