Version Control System, Git and GitHub Collaboration

1. Introduction to Version Control Systems

Git's three-tree architecture (Working Directory, Staging Area, Repository)

What is Version Control?

A system that records changes to files over time, allowing you to:

✔ Track modifications to your code
✔ Revert to previous versions when needed
✔ Collaborate efficiently with team members
✔ Maintain different versions of your project

Types of Version Control

Type	Description	Example	When to Use
Local	Tracks changes on a single machine	RCS, SCCS	Individual projects with no need for collaboration
Centralized	Single server hosts all versions	SVN, CVS	Small teams with centralized infrastructure
Distributed	Every user has a full repository copy	Git, Mercurial	Modern development (teams, open source, etc.)

Why Git?

93% of developers use Git (Stack Overflow Survey 2021)
Enables non-linear workflows through branching and merging
Fully decentralized - work offline and sync later
Lightweight and extremely fast
Integrates with all modern development tools

2. Git Fundamentals

Git file lifecycle - from untracked to committed

Key Concepts

Repository: Your project folder tracked by Git
Commit: A snapshot of your changes with a descriptive message
Branch: An isolated line of development
Merge: Combining branches together
Remote: A hosted repository (e.g., on GitHub)
Staging Area: Where you prepare changes before committing

Essential Commands

1. Setup & Basics

Initialize a new repository

git init

Creates a new .git directory in your project

Clone an existing repository

git clone https://github.com/user/repo.git

Downloads the entire repository with history

Check repository status

git status

Shows changed, staged, and untracked files

2. Making Changes

Stage specific files

git add index.html styles.css

Prepares specific files for committing

Stage all changes

git add .

Prepares all modified and new files

Commit staged changes

git commit -m "Add user login functionality"

Creates a permanent snapshot with a message

Commit Message Guidelines:

Limit to 50 characters for the subject line
Use imperative mood ("Add" not "Added")
Explain what and why (not how)

3. Branching

List all branches

git branch

Shows local branches (* marks current)

Create and switch to new branch

git checkout -b feature/login

Creates branch and moves HEAD to it

Switch between branches

git checkout main

Moves HEAD to specified branch

Merge branches

git merge feature/login

Combines feature/login into current branch

Modern Git Alternative

Git 2.23+ introduced git switch and git restore:

git switch -c new-feature  # Create and switch
git switch main        # Switch branches

4. Undoing Changes

Undo last commit (keep changes)

git reset --soft HEAD~1

Moves HEAD back but keeps changes staged

Discard file changes

git checkout -- index.html

Reverts file to last committed state

Create undo commit

git revert a1b2c3d

Safely reverses a specific commit

Dangerous Reset

git reset --hard HEAD~3

This will permanently delete the last 3 commits and all their changes. Use with extreme caution!

5. Viewing History

Compact log with graph

git log --oneline --graph --all

Visualizes branch structure

See changes in commits

git show abc123

Displays full details of a commit

Compare branches

git diff main..feature

Shows all differences between branches

3. GitHub Collaboration

GitHub Workflow

Fork the repository

Clone your fork locally:

git clone https://github.com/your-username/repo.git

Add upstream (original repo):

git remote add upstream https://github.com/original-owner/repo.git

Sync with upstream:

git fetch upstream
git merge upstream/main

Pull Requests (PRs)

Create PRs to propose changes to original projects
Resolve merge conflicts if they occur
Use GitHub Issues to track bugs/enhancements

Open Source Contribution

✔ Start with good-first-issue labeled tasks
✔ Follow project guidelines (CONTRIBUTING.md)
✔ Keep commits small and focused

4. Practical Task: Branch Creation & Submission

Task Instructions

Fork the test repository:
https://github.com/ShMazumder/test-examples
Create a branch named after your GitHub username:
```
git checkout -b your-username
```
Make changes (e.g., add a file with your name)
Push your branch:
```
git push origin your-username
```
Create a Pull Request to the original repository

Important: Your branch name must exactly match your GitHub username for verification.

Verification Form

5. Best Practices & Workflow

Git Hygiene

Write descriptive commit messages (e.g., "Fix login button alignment")
Commit often, push logically related changes together
Use .gitignore to exclude unnecessary files

Branching Strategies

Strategy	Use Case
Feature Branches	New functionality (e.g., `feat/user-auth`)
Hotfix Branches	Critical bug fixes
Git Flow	Complex projects with versions

CI/CD Integration

Automate testing with GitHub Actions:

name: Node.js CI
on: [push]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - run: npm install && npm test

Next Steps

Practice daily with small projects
Contribute to open-source repositories
Explore advanced Git features (rebase, submodules)

Pro Tip: Maintain a DEVLOG.md to document your learning journey!