py-vcs-lite 0.1.1

A lightweight Git-like version control system

vcs - A Lightweight Git-like Version Control System

A simple, educational version control system implemented in Python that demonstrates the core concepts behind Git. Perfect for learning how version control systems work internally.

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📋 Table of Contents

• Overview
• Features
• Installation
• Commands
• Usage Examples
• Project Structure
• How It Works
• Contributing
• License

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🎯 Overview

vcs is a minimal version control system that implements the fundamental concepts of Git in a simplified manner. It provides content tracking through blob and tree objects, commit history with parent-child relationships, staging area for preparing commits, and basic authentication for access control.

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🧰 Features

• Repository initialization (vcs init)
• User authentication (vcs auth)
• File staging (vcs add)
• Commit creation (vcs commit)
• History viewing (vcs log)
• Commit inspection (vcs show)
• Version checkout (vcs checkout)
• Compressed storage using zlib for efficient space usage
• Content-based addressing with SHA-1 hashing

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📦 Installation

Local Installation

# Clone the repository
git clone https://github.com/yourusername/vcs.git
cd vcs

# Install the package
pip install .

Verify Installation

vcs --help

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📖 Commands

vcs init

Initialize a new VCS repository in the current directory.

vcs init

How it works:

• Creates a .vcs/ directory with necessary subdirectories (objects, commits, etc.)
• Sets up essential files like HEAD and index to start tracking
• Establishes the foundation for version control in your project

vcs auth <username> <email>

Set user credentials that will be stored in the config file.

vcs auth john_doe [e-mail]

How it works:

• Stores the username and email in .vcs/config for subsequent operations
• Required for commit operations to identify the author

vcs add <file>

Stage a file for the next commit.

vcs add filename.txt

How it works:

• Stages changes by hashing the file's contents into a blob object
• Updates the index to track the file and its hash (prepares for commit)
• Think of this as telling VCS: "I want this file to be part of the next commit"

vcs commit "<message>"

Create a new commit with staged changes.

vcs commit "Initial commit"

How it works:

• Creates a new commit object with:
  • A tree object representing the snapshot of all files staged (from the index)
  • Metadata like the commit message, author, timestamp
• Stores the commit object compressed in .vcs/objects
• Updates HEAD to point to this new commit hash
• Saves the snapshot, so you can revert or checkout later

vcs log

Display the commit history.

vcs log

How it works:

• Shows the history of commits starting from HEAD
• Displays chronological list with hash, author, timestamp, and message
• Useful to track changes over time and review commit messages

vcs show <commit_hash>

Show detailed information about a specific commit.

vcs show a1b2c3d4
# or
vcs show HEAD

How it works:

• Retrieves the commit object from storage
• Displays commit metadata and associated file changes
• Helps you understand what changed in a specific commit

vcs checkout <commit_hash>

Switch the working directory to a specific commit.

vcs checkout a1b2c3d4

How it works:

• Switches your working directory to reflect the snapshot of the specified commit
• Deletes files that don't exist in the commit and restores files from the commit tree
• Updates HEAD to point to the commit
• Allows you to view or work with your project at any point in history

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💡 Usage Examples

Basic Workflow

# Initialize repository
vcs init

# Set user credentials
vcs auth alice [e-mail]

# Create and add a file
echo "Hello World" > hello.txt
vcs add hello.txt

# Commit the changes
vcs commit "Add hello.txt"

# Make changes and commit again
echo "Updated content" >> hello.txt
vcs add hello.txt
vcs commit "Update hello.txt"

# View history
vcs log

# Check out previous version
vcs checkout <first_commit_hash>

Working with Multiple Files

# Add multiple files
echo "File 1" > file1.txt
echo "File 2" > file2.txt
vcs add file1.txt
vcs add file2.txt
vcs commit "Add two files"

# Show latest commit details
vcs show HEAD

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📁 Project Structure

project/
├── .vcs/                    # VCS repository data
│   ├── objects/             # Compressed blob and tree objects
│   ├── commits/             # Commit objects
│   ├── index                # Staging area
│   ├── HEAD                 # Current commit reference
│   └── config               # Authentication and settings
└── vcs/                     # Source code
    ├── __init__.py
    ├── main.py             # CLI entry point
    └── commands/           # Command implementations
        ├── init.py
        ├── auth.py
        ├── add.py
        ├── commit.py
        ├── log.py
        ├── show.py
        └── checkout.py

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🔍 How It Works

Object Storage

• Blobs: Store file contents, compressed with zlib
• Trees: Store directory structures and file metadata
• Commits: Store commit metadata and tree references

Authentication

• Username and email stored in .vcs/config
• Required for commit operations
• Set once using vcs auth <username> <email>

Data Flow

1. Add: File content → Blob object → Index entry
2. Commit: Index entries → Tree object → Commit object → Update HEAD
3. Checkout: Commit hash → Tree object → Restore files

File Organization

.vcs/
├── objects/           # Content-addressable storage
├── commits/           # Commit metadata
├── index              # Staging area (JSON)
├── HEAD               # Current commit pointer
└── config             # User credentials

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🤝 Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Test thoroughly
5. Submit a pull request

Code Style

• Follow PEP 8
• Use meaningful variable names
• Add docstrings for functions
• Include error handling

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📄 License

MIT License

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Author: Arjun

Thank you for using VCS!