Git Internals

# Git Internals PRD

## Overview
Implement git's core object model including content-addressable blob, tree, and commit objects with SHA-1 hashing, zlib compression, ref management, and basic porcelain commands for init, commit, log, branch, checkout, status, and diff.

## Requirements
- Content-addressable object storage using SHA-1 hashes as keys
- Blob objects storing raw file content
- Tree objects storing directory listings that map names to blob or tree hashes
- Commit objects containing tree hash, parent hash, author info, message, and timestamp
- Object serialization and deserialization matching git's format
- Zlib compression for all stored objects
- init command that creates the .mini-git directory structure
- hash-object command that stores a file as a blob and prints its hash
- cat-file command that reads and displays any object by its hash
- write-tree command that creates a tree object from the current working directory
- commit-tree command that creates a commit pointing to a tree with a message
- update-ref command that creates or updates branch references
- log command that walks commit parents and displays the commit history
- Branch creation by creating a ref under refs/heads/
- checkout that updates the working directory from a commit's tree
- status that compares the working directory to the HEAD tree
- diff between two commits showing changed files

## Tech Stack
- TypeScript / Node.js
- Crypto module for SHA-1 hashing, zlib module for compression
- No external git libraries — raw object format implementation required

## Scoring Criteria
- **Functional (40%)**: Objects store and retrieve correctly, commits chain properly, log displays history
- **Quality (20%)**: Correct git object format, proper hash computation, clean code structure
- **Fidelity (25%)**: All commands work including checkout, status, diff, and branch management
- **Speed (15%)**: Time bonus