feat: Add comprehensive Git integration with proper gix API implementation and user documentation

[zhangfengcdt]

Implements complete Git integration for ProllyTree, enabling versioned key-value operations with full Git compatibility.

Key Features

• VersionedKvStore: Core integration combining ProllyTree with Git repositories
• GitNodeStorage: Stores ProllyTree nodes as Git blobs with content-addressable hashing
• GitOperations: Provides merge, diff, show, and revert operations for KV data
• CLI Tool: git-prolly command-line interface for Git-aware KV operations

Technical Implementation

• Uses gix library for Git operations with proper object handling
• Implements three-way merge algorithm for conflict resolution
• Provides comprehensive error handling and type safety
• Maintains full Git compatibility
• works with standard Git tools

Benefits

• Version Control: Full history tracking and branching for KV data
• Collaboration: Standard Git workflows (push, pull, clone, merge)
• Integrity: Content-addressable storage ensures data consistency
• Tooling: Compatible with existing Git ecosystem

Testing

• Comprehensive unit tests for all components
• Integration tests for Git operations

Ready for production use with complete documentation and examples.

Basic Operations

  # Initialize git-prolly repository
  git-prolly init

  # KV operations
  git-prolly set user:123 "John Doe"
  git-prolly set config:theme "dark"
  git-prolly commit -m "Initial data"

  # Git integration
  git log --oneline  # Standard Git commands work
  git push origin main  # Full Git hosting support

  Advanced Workflows

  # Branching and merging
  git-prolly branch feature/preferences
  git-prolly checkout feature/preferences
  git-prolly set pref:notifications "enabled"
  git-prolly commit -m "Add preferences"
  git-prolly checkout main
  git-prolly merge feature/preferences

  # History and diffs
  git-prolly log --kv-summary
  git-prolly diff main feature/preferences
  git-prolly show HEAD --keys-only