Add directory replication support

[corylanou]

Summary

This PR implements directory replication support, allowing Litestream to replicate entire directories of SQLite databases. This is particularly useful for multi-tenant applications where each tenant has their own database file.

Closes #42

Features

• 📁 Scan directories for SQLite databases with configurable file patterns (*.db, *.sqlite, etc.)
• 🔄 Support for recursive directory scanning to find databases in subdirectories
• ✅ Validate files by checking SQLite headers (prevents replicating non-SQLite files)
• 🎯 Mix single database and directory configurations in the same config file

Configuration Example

dbs:
  # Replicate all databases in a directory
  - directory: /var/lib/myapp/databases
    pattern: "*.db"        # optional, defaults to "*.db"
    recursive: true        # optional, defaults to false
    replica:
      type: s3
      bucket: my-bucket
      path: backups

  # Can still use single database configs alongside
  - path: /var/lib/critical/main.db
    replica:
      type: s3
      bucket: critical-backups
      path: main

Implementation Details

• Extended DBConfig with Directory, Pattern, and Recursive fields
• Added NewDBsFromDirectoryConfig() to create multiple DB instances from a directory
• Added FindSQLiteDatabases() for directory scanning with pattern matching
• Added IsSQLiteDatabase() for file validation via header check
• Updated ReplicateCommand to handle directory configurations
• Added comprehensive test coverage in main_test.go

Testing

• ✅ All existing tests pass
• ✅ Added tests for directory scanning functionality
• ✅ Added tests for SQLite file detection
• ✅ Added tests for configuration validation
• ✅ go vet passes
• ✅ staticcheck passes

Example Configuration

See etc/litestream-directory-example.yml for comprehensive examples including multi-tenant and mixed configurations.

Documentation Follow-up

A follow-up issue should be created in the litestream.io repository to document:

• New configuration options (directory, pattern, recursive)
• Use cases for multi-tenant applications
• Examples of mixed single/directory configurations
• Current limitations (no dynamic discovery without restart, shared config for all DBs in directory)

Future Enhancements

• Dynamic database discovery (add/remove databases without restart)
• Per-database override configurations within a directory
• Automatic cleanup of removed databases from replicas

🤖 Generated with Claude Code

Co-Authored-By: Claude noreply@anthropic.com