Version Control with Git and GitHub - Introduction to Software Engineering

Version Control with Git and GitHub¶

Welcome to the world of modern software collaboration! Today we’ll explore how Git and GitHub revolutionize the way developers work together.

Why Version Control?¶

The Problem

The Solution

Figure 1:“If that doesn’t fix it, git.txt contains the phone number of a friend of mine who understands git. Just wait through a few minutes of ‘It’s really pretty simple, just think of branches as...’ and eventually you’ll learn the commands that will fix everything.” - XKCD

Before Version Control:

project_final.zip
project_final_v2.zip
project_final_REALLY_final.zip
project_final_use_this_one.zip

Git vs GitHub: Understanding the Difference¶

Git - Local Version Control

Local Version Control System

Runs on your computer
Tracks file changes
Manages project history
Works offline
Command-line tool

GitHub - Cloud Platform

Cloud-Based Git Hosting

Remote repository storage
Web-based interface
Collaboration features
Issue tracking
Project management tools

Git Fundamentals¶

The Three Trees of Git¶

Git organizes your work into three main areas, each serving a specific purpose in the version control workflow.

Working Directory

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Your current project files

What it contains:

Modified files
New files
Deleted files

Staging Area

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Prepared changes for commit

What it contains:

Files ready to be committed
Snapshot of selected changes

Repository

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Permanent project history

What it contains:

All committed changes
Complete project timeline
Branch information

Essential Git Commands¶

Table 1:Git Command Reference

Command	Purpose	Example	When to Use
`git init`	Initialize repository	`git init my-project`	Starting a new project
`git clone`	Copy remote repository	`git clone https://github.com/user/repo.git`	Working on existing project
`git add`	Stage changes	`git add filename.txt`	Before committing changes
`git commit`	Save changes permanently	`git commit -m "Add new feature"`	After staging changes
`git push`	Upload to remote	`git push origin main`	Sharing your work
`git pull`	Download from remote	`git pull origin main`	Getting latest changes

Hands-On Exercise: Your First Repository¶

:class: important

Follow along as we create your first Git repository. Open your terminal and let’s go!


### Step 1: Initial Setup

```{code-block} bash
:caption: Configure Git (do this once per computer)
:linenos:

# Set your identity
git config --global user.name "Your Name"
git config --global user.email "your.email@example.com"

# Check your configuration
git config --list

:class: tip

Use the same email address you’ll use for GitHub to link your commits to your GitHub profile!


### Step 2: Create Your First Repository

```{code-block} bash
:caption: Initialize a new repository
:linenos:
:emphasize-lines: 3,6

# Create a new directory
mkdir my-first-repo
cd my-first-repo

# Initialize Git repository
git init

# Check status
git status

Step 3: Add and Commit Files¶

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# Create a README file
echo "# My First Repository" > README.md
echo "This is my introduction to Git!" >> README.md

# Check what changed
git status

# Stage the file
git add README.md

# Check status again
git status

# Commit the changes
git commit -m "Initial commit: Add README"

Create and track your first file

🌿 Understanding Branches¶

Branching Workflow Visualization¶

Common Branching Commands¶

Creating Branches

Working with Branches

Cleaning Up

# Create a new branch
git branch feature/new-feature

# Switch to the branch
git checkout feature/new-feature

# Create and switch in one command
git checkout -b feature/another-feature

# List all branches
git branch

Branch creation and switching

# Make changes to files
echo "New feature code" > feature.txt

# Stage and commit
git add feature.txt
git commit -m "Add new feature"

# Switch back to main
git checkout main

# Merge the feature branch
git merge feature/new-feature

Making changes on branches

# Delete a merged branch (local)
git branch -d feature/new-feature

# Force delete a branch (be careful!)
git branch -D feature/unwanted-feature

# Delete remote branch
git push origin --delete feature/old-feature

Branch maintenance

🐙 GitHub: Collaboration Supercharged¶

Repository Features¶

Issues & Project Management

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Bug tracking
Feature requests
Project boards
Milestone planning

## Bug Report

**Description:** Brief description of the bug

**Steps to Reproduce:**
1. Go to '...'
2. Click on '....'
3. See error

**Expected behavior:** What should happen
**Actual behavior:** What actually happens

Sample Issue Template

Pull Requests

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Code review process
Discussion threads
Automated testing
Merge management

## Changes Made
- [ ] Added login functionality
- [ ] Updated documentation  
- [ ] Added unit tests

## Testing
- All tests pass ✅
- Manual testing completed ✅

Sample PR Template

GitHub Workflow Exercise¶

Exercise 1 (Create Your GitHub Repository)

Create a GitHub account (if you don’t have one)
Create a new repository called “git-practice”

Clone it locally:

git clone https://github.com/yourusername/git-practice.git

Add a README file with your name and course information

Push your changes:

git add README.md
git commit -m "Add personal README"
git push origin main


## 🤝 Collaboration Workflows

### The GitHub Flow

```{mermaid}
graph TD
    A[Create Branch] --> B[Make Changes]
    B --> C[Create Pull Request]
    C --> D[Code Review]
    D --> E{Approved?}
    E -->|Yes| F[Merge to Main]
    E -->|No| B
    F --> G[Deploy]
    
    style A fill:#e1f5fe
    style F fill:#c8e6c9
    style G fill:#fff3e0

Best Practices for Collaboration¶

Good commit messages are:

type(scope): short description

Longer description explaining the change
and why it was necessary.

- Bullet points for multiple changes
- Reference issues: Fixes #123

Commit Message Format

Examples:

feat(auth): add user login functionality

fix(api): resolve null pointer exception in user service

docs(readme): update installation instructions

test(auth): add unit tests for login validation

Good Commit Messages

Step-by-Step PR Process:

Create a feature branch:

git checkout -b feature/user-authentication

Make your changes and commit:

git add .
git commit -m "feat(auth): implement user login system"

Push to GitHub:

git push origin feature/user-authentication

Create Pull Request on GitHub
Request reviewers
Address feedback
Merge when approved

🚨 Common Git Scenarios & Solutions¶

Merge Conflicts

Undoing Changes

Viewing History

Example conflict:

<<<<<<< HEAD
function greet() {
    return "Hello World!";
}
=======
function greet() {
    return "Hi there!";
}
>>>>>>> feature-branch

Merge conflict in code

Resolution steps:

Open the conflicted file
Choose which version to keep (or combine them)
Remove conflict markers (<<<<<<<, =======, >>>>>>>)
Add and commit the resolved file

# Undo changes in working directory
git checkout -- filename.txt

# Unstage a file
git reset HEAD filename.txt

# Undo last commit (keep changes)
git reset --soft HEAD~1

# Undo last commit (discard changes)
git reset --hard HEAD~1

# Create a new commit that undoes changes
git revert HEAD

Common undo operations

# View commit history
git log

# View compact history
git log --oneline

# View graphical history
git log --graph --all --oneline

# View changes in a commit
git show <commit-hash>

# View file history
git log --follow filename.txt

Exploring project history

Interactive Quiz¶

Advanced GitHub Features¶

GitHub Actions (CI/CD Preview)¶

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name: Test and Deploy

on:
  push:
    branches: [ main ]
  pull_request:
    branches: [ main ]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v2
    - name: Setup Node.js
      uses: actions/setup-node@v2
      with:
        node-version: '16'
    - run: npm install
    - run: npm test

Simple GitHub Actions workflow

Project Management with GitHub¶

GitHub Project Features

Feature	Purpose	Best For
Issues	Track bugs and features	Task management
Projects	Kanban-style boards	Sprint planning
Milestones	Group related issues	Release planning
Discussions	Community conversations	Q&A and brainstorming

Practice Challenges¶

📚 Resources & Next Steps¶

Essential Resources¶

📖 Documentation

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🎮 Interactive Learning

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Cheat Sheets¶

Basic Workflow:

git status                 # Check status
git add <file>            # Stage file
git add .                 # Stage all files
git commit -m "message"   # Commit changes
git push origin main      # Push to remote
git pull origin main      # Pull from remote

Branching:

git branch                # List branches
git branch <name>         # Create branch
git checkout <name>       # Switch branch
git checkout -b <name>    # Create and switch
git merge <branch>        # Merge branch
git branch -d <name>      # Delete branch


## **Key Takeaways**

```{admonition} 🏁 What You've Learned Today
:class: success

✅ **Version Control Fundamentals**
- Why version control is essential for software development
- The difference between Git and GitHub

✅ **Git Basics**
- Essential Git commands and workflows
- The three trees: Working Directory, Staging Area, Repository

✅ **Branching Strategies**
- How to create, switch, and merge branches
- Best practices for branch naming and management

✅ **GitHub Collaboration**
- Pull Request workflow
- Code review process
- Project management features

✅ **Real-World Skills**
- Handling merge conflicts
- Writing good commit messages
- Using GitHub for team collaboration

🔜 Coming Up Next¶

In our next lecture, we’ll explore the Software Development Life Cycle (SDLC) and see how version control fits into the bigger picture of software engineering processes.

“Git is not just a tool, it’s a way of thinking about collaboration and code evolution.”

Introduction to Software Engineering

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