Java Git - Version Control System (VCS)

A robust, extensible version control system implementation in Java that provides core version control functionality including file tracking, versioning, diffing, and merge conflict resolution.

Features

• File Management

  • Track and Untrack files
  • Monitor file status changes (modified, deleted, staged)
  • Support for binary and text files
  • Automatic file hash calculation and verification

• Version Control

  • Create versions with commit messages
  • Maintain version history
  • Revert to previous versions
  • Track version metadata (author, timestamp, file hashes)

• Diff Generation

  • Line-by-line diff analysis
  • Support for additions, deletions, and modifications
  • Efficient diff algorithm using dynamic programming
  • Generate diffs between versions or working changes

• Merge Handling

  • Detect and resolve merge conflicts
  • Multiple conflict resolution strategies (keep source, keep target, custom)
  • Automatic merging for non-conflicting changes
  • Detailed conflict information tracking

Architecture

The system is built using a modular architecture with clear separation of concerns:

Core Components

• VersionControlSystem: Main entry point and coordinator
• FileTracker: Handles file status monitoring and tracking
• VersionManager: Manages version creation and history
• DiffGenerator: Generates and compares file differences
• MergeHandler: Handles merge operations and conflict resolution

Key Interfaces

• Trackable: File tracking operations
• Versionable: Version management operations
• Diffable: Diff generation operations
• Mergeable: Merge handling operations
• Uploadable: File upload operations

Models

• VersionInfo: Version metadata and file hashes
• FileMetadata: File tracking information
• ChangedLines: Diff information
• ConflictInfo: Merge conflict details
• LineChange: Individual line modifications

Getting Started

Prerequisites

• Java 23 or higher
• IntelliJ IDEA (Community or Ultimate Edition)

Installation

1. Clone the repository:

git clone https://github.com/yourusername/vcs.git

2. Open the project in IntelliJ IDEA:

   • Launch IntelliJ IDEA
   • Select File -> Open
   • Navigate to the cloned repository directory
   • Click OK to open the project
   • Wait for IntelliJ to finish importing and indexing the project

3. Configure Project SDK:

   • Right-click the project root in the Project view
   • Select Module Settings (F4)
   • Under Project, ensure the Project SDK is set to Java 17 or higher
   • Click OK to apply the changes

4. Build the project:

   • Select Build -> Build Project or press Ctrl+F9 (⌘F9 on macOS)

Basic Usage

1. Initialize a new VCS repository:

VersionControlSystem vcs = new VersionControlSystem("/path/to/repository");

2. Track files:

vcs.trackFile("myfile.txt");

3. Create a version:

String versionId = vcs.createVersion("Initial commit");

4. Generate diff:

DiffResult diff = vcs.getDiffGenerator().getDiff("oldVersion", "newVersion");

5. Handle merge conflicts:

boolean merged = vcs.getMergeHandler().merge("sourceVersion", "targetVersion");
if (!merged) {
    List<ConflictInfo> conflicts = vcs.getMergeHandler().getConflicts();
    // Handle conflicts
}

Error Handling

The system uses a hierarchical exception system:

• VCSException: Base exception class
• FileOperationException: File-related errors
• VersionException: Version-related errors
• MergeConflictException: Merge-related errors

Each exception type includes specific subclasses for detailed error handling.

Testing

The project includes comprehensive tests:

• Unit tests for all components
• Integration tests for workflows
• Concurrency tests
• Edge case handling
• Error condition testing

Run tests using:

• Right-click on the test directory in the Project view
• Select Run 'All Tests'
• Or use the keyboard shortcut Ctrl+Shift+F10 (⌘Shift+F10 on macOS)

Design Patterns Used

• Observer Pattern: File change notifications
• Strategy Pattern: Diff algorithms and merge strategies
• Factory Pattern: Exception creation
• Builder Pattern: Version creation
• Command Pattern: File operations

Acknowledgments

• The diff algorithm is inspired by the Myers diff algorithm
• File hashing uses SHA-256 for content verification
• Conflict resolution approach based on modern VCS systems