My_Own_Git

A custom implementation of Git's core functionality from scratch using Python. Learn how version control actually works under the hood.

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🎯 Project Overview

This project replicates Git's essential features by building a version control system from the ground up. Instead of using Git's C implementation, this is a pure Python implementation designed to teach and demonstrate how modern VCS (Version Control Systems) work internally.

What you'll learn:

• How commits, branches, and merge algorithms work
• Object storage and compression in version control
• DAG (Directed Acyclic Graph) structures
• Content-addressable storage using hashing
• Merge conflict resolution

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✨ Features

• ✅ Repository initialization — Create local .mygit directories
• ✅ Commit system — Store snapshots with SHA-1 hashing
• ✅ Branching — Create, switch, and list branches
• ✅ Merge operations — Fast-forward and recursive merges
• ✅ Status tracking — Monitor staged and unstaged changes
• ✅ Diff visualization — Compare versions
• ✅ Revert functionality — Undo commits safely

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🚀 Quick Start

Installation

git clone https://github.com/devberatzengin/My_Own_Git.git
cd My_Own_Git
python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate
pip install -r requirements.txt

Basic Commands

# Initialize a repository
python mygit.py init

# Stage changes
python mygit.py add <file>

# Create a commit
python mygit.py commit -m "Your message"

# Create a branch
python mygit.py branch <branch-name>

# Switch branches
python mygit.py checkout <branch-name>

# Merge branches
python mygit.py merge <branch-name>

# View status
python mygit.py status

# View history
python mygit.py log

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📁 Project Structure

My_Own_Git/
├── mygit.py              # Main entry point
├── core/
│   ├── objects.py        # Commit, Tree, Blob classes
│   ├── repository.py     # Repository management
│   ├── staging.py        # Index/staging area
│   └── merge.py          # Merge algorithms
├── cli/
│   └── commands.py       # CLI interface
├── utils/
│   ├── hash.py           # SHA-1 hashing
│   └── diff.py           # File diffing
├── tests/
│   ├── test_commits.py
│   ├── test_merge.py
│   └── test_branches.py
└── requirements.txt

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🔧 Technical Details

Architecture

Object Model:

• Blob — File content (immutable)
• Tree — Directory snapshot
• Commit — Metadata + parent reference + tree
• Ref — Pointer to commit (branch/tag)

Storage:

.mygit/
├── objects/              # Content-addressable storage
│   ├── <hash[0:2]>/
│   │   └── <hash[2:]>   # Zlib-compressed object
├── refs/
│   ├── heads/           # Branch pointers
│   └── tags/            # Tag pointers
└── HEAD               # Current branch reference

Merge Algorithm:

• Three-way merge for automatic resolution
• Conflict markers for manual cases
• Recursive history traversal using LCA (Lowest Common Ancestor)

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📊 How It Works: Internal Flow

User creates file → Add to staging → Commit
                      ↓
              Create blob + tree
                      ↓
           Hash objects + store in .mygit/objects
                      ↓
          Update branch ref to new commit SHA
                      ↓
            Update HEAD if on that branch

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🧪 Testing

# Run all tests
python -m pytest tests/ -v

# Run specific test
python -m pytest tests/test_commits.py -v

# With coverage
pytest --cov=core tests/

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📚 Key Learning Outcomes

After studying this project, you'll understand:

1. How Git stores data — Content-addressable storage model
2. Commit structure — Snapshots vs. deltas
3. Branch mechanics — Just pointers to commits
4. Merge algorithms — Three-way merge + conflict detection
5. Performance — Why Git is fast (DAGs, compression)

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🤔 Future Enhancements

• Remote repositories (push/pull simulation)
• Rebase functionality
• Cherry-pick operations
• Stash management
• Hook system (pre-commit, post-commit)
• Performance optimization with C extensions

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💡 References

• Git Internals - Git Book
• Linus Torvalds' Original Design
• Mercurial's Revlog Format

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🤝 Contributing

Found a bug or want to improve the merge algorithm? Pull requests are welcome!

1. Fork the repository
2. Create your feature branch (git checkout -b feature/improvement)
3. Commit your changes (git commit -m 'Add improvement')
4. Push to the branch (git push origin feature/improvement)
5. Open a Pull Request

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📧 Questions?

Open an issue or reach out on LinkedIn