Git & GitHub: From Zero to Pro

A comprehensive guide to learn Git and GitHub from scratch.

📌 What is Git & GitHub?

Git is a version control system that tracks changes in your code. Think of it as a time machine for your project — you can save snapshots (called commits) and travel back to any previous version.

GitHub is a cloud service that lets you save your Git repositories online. It helps you:

🔒 Backup your code in case you lose it locally
📜 View history of all code changes easily
👥 Collaborate with teammates through pull requests

Key Terms

Repository (Repo) = A folder containing code where changes are tracked by Git
Local Repository = A Git repository saved on your computer
Remote Repository = A Git repository saved online (e.g., on GitHub)

🖥️ Command Line Basics

Before diving into Git, you need to know these basic terminal commands:

Command	Description
`ls`	List all files and folders in the current directory
`cd ~/Desktop/folder`	Change to a different directory

Important

All Git commands must be run inside the folder that contains your code.

⚙️ Initial Configuration

Before making commits, configure your identity:

bash

# Set your name for commits
git config --global user.name "Your Name"

# Set your email for commits
git config --global user.email "your.email@example.com"

# Enable colorful output (optional but helpful)
git config --global color.ui auto

📦 Creating Commits

In Git:

Version = Commit
Version History = Commit History

Initialize a Repository

bash

# Start tracking changes in the current folder
git init

# Check current status (shows changes since last commit)
git status

Stage Changes (Add to Staging Area)

bash

# Add a specific file
git add filename.txt

# Add all files in a folder (and subfolders)
git add folder/

# Add ALL changed files
git add .

Create a Commit

bash

# Create a commit with a message
git commit -m "Your descriptive message here"

# Update the previous commit (instead of creating a new one)
git commit -m "Updated message" --amend

View Commit History

bash

# View commit history
git log

# View ALL commits (including other branches)
git log --all

# View commits with visual branching graph
git log --all --graph

🔄 Understanding Git Areas

Git has three main areas where your code lives:

┌─────────────────┐     git add      ┌─────────────────┐    git commit    ┌─────────────────┐
│  Working Area   │ ───────────────► │  Staging Area   │ ───────────────► │ Commit History  │
│ (Your changes)  │                  │ (Ready to save) │                  │   (Saved!)      │
└─────────────────┘                  └─────────────────┘                  └─────────────────┘
                     ◄───────────────
                        git reset

Moving Between Areas

bash

# Working → Staging
git add .

# Staging → Commit History
git commit -m "message"

# Staging → Working (unstage changes)
git reset file
git reset folder/
git reset .

# Discard changes in working area
git checkout -- file
git checkout -- folder/
git checkout -- .

⏪ Viewing Previous Commits

bash

# View a specific commit
git checkout <commit_hash>

# View the latest commit of a branch
git checkout <branch_name>

Understanding HEAD and Branches

HEAD = Points to the commit you are currently viewing
Branch (e.g., main, master) = Always points to the latest commit on that branch

Example commit history:

commit 81491250a2a940babba4a3f69bec7aa2c87b782a (master)
Author: Your Name <your.email@example.com>
Date: Sat Feb 20 07:19:11 2021
    Version 3

commit 4fb1b33d86a825c517b0376ebd950111f98d0ada
Author: Your Name <your.email@example.com>
Date: Sat Feb 20 07:18:53 2021
    Version 2

commit 400e1ba797f732c94e290774aacfd4738c864db8 (HEAD)
Author: Your Name <your.email@example.com>
Date: Sat Feb 20 05:49:00 2021
    Version 1

🔧 Restoring to a Previous Commit

bash

# Restore a specific file to a previous commit
git checkout <hash> file

# Restore all files in a folder
git checkout <hash> folder/

# Restore entire project to a previous commit
git checkout <hash> .

🛠️ Other Useful Git Features

Create Shortcuts (Aliases)

bash

# Create an alias
git config --global alias.s "status"

# Now you can use: git s (instead of git status)

Ignore Files

Create a .gitignore file to tell Git which files/folders to ignore:

bash

# Example .gitignore content
node_modules/
.env
*.log

Remove Git from a Project

bash

# Completely remove Git tracking
rm -rf .git

☁️ Uploading Code to GitHub

Link Local to Remote Repository

bash

# Link your local repo to a GitHub repo
git remote add origin https://github.com/username/repository.git

# List all linked remote repositories
git remote

# List with more detail
git remote -v

# Remove a remote link
git remote remove origin

Configure GitHub Credentials

bash

# Set your GitHub username
git config --global credential.username your-username

Push Code to GitHub

bash

# Upload a branch to remote repository
git push origin main

# Set up shortcut for future pushes
git push origin main --set-upstream

# Now you can just use:
git push

# Force push (overwrites remote — use with caution!)
git push origin main -f

⬇️ Downloading Code from GitHub

Clone a Repository

bash

# Download a repository
git clone https://github.com/username/repository.git

# Download with a custom folder name
git clone https://github.com/username/repository.git my-folder

Fetch and Pull Updates

bash

# Update remote tracking branches (doesn't modify your files)
git fetch

# Download AND merge updates from remote
git pull origin main

# Set up shortcut for future pulls
git pull origin main --set-upstream

git pull = git fetch + git merge

git pull downloads new commits AND merges them into your local branch automatically.

🌿 Branching

Branching creates a copy of your version history that you can work on without affecting the original. This lets you work on multiple features simultaneously!

bash

# List all branches
git branch

# Create a new branch
git branch feature1

# Switch to a branch
git checkout feature1

# Create AND switch to a new branch (shortcut)
git checkout -b feature1

# Delete a branch
git branch -D feature1

Understanding HEAD with Branches

* commit 9bb22ff (HEAD -> feature1, master)
|   Version 3
|
* commit 8464f5b
|   Version 2
|
* commit 285addb
    Version 1

HEAD -> feature1 means you're currently on the feature1 branch. New commits will be added to this branch.

🔀 Merging Branches

Merging combines changes from one branch into another:

bash

# First, switch to the branch you want to merge INTO
git checkout main

# Then merge another branch into it
git merge feature1 -m "Merge feature1 into main"

⚠️ Merge Conflicts

A merge conflict happens when Git doesn't know which changes to keep (e.g., two branches modified the same line).

What a Conflict Looks Like

<<<<<<< HEAD
code from current branch
=======
code from branch being merged
>>>>>>> feature1

How to Resolve

Edit the file — delete the conflict markers and keep the code you want:

bash

# Before (conflict)
<<<<<<< HEAD
console.log("Hello");
=======
console.log("Hi there!");
>>>>>>> feature1

# After (resolved)
console.log("Hi there!");

Repeat for all conflicts in all files
Create a commit to save the resolution:

bash

git add .
git commit -m "Resolved merge conflicts"

🚀 Feature Branch Workflow

This is a popular workflow used by professional development teams:

Step 1: Create a Feature Branch

bash

git branch new-feature
git checkout new-feature

Step 2: Make Changes and Commit

bash

# Make your code changes, then...
git add .
git commit -m "Add new feature"

Step 3: Push Feature Branch to GitHub

bash

git push origin new-feature

Step 4: Create a Pull Request

On GitHub, create a Pull Request (PR) to let teammates review your code.

Step 5: Merge the Pull Request

After approval, click "Merge pull request" on GitHub.

Step 6: Update Local Repository

bash

git checkout main
git pull origin main

🔥 Handling Merge Conflicts in Feature Branches

If two PRs modify the same file/line, you'll get a merge conflict.

Option 1: Resolve on GitHub

GitHub provides a web editor to resolve simple conflicts.

Option 2: Resolve Locally

bash

# 1. Get latest updates from main
git checkout main
git pull origin main

# 2. Get latest updates from feature branch
git checkout feature-branch
git pull origin feature-branch

# 3. Merge main INTO your feature branch
git merge main

# 4. Resolve conflicts in your editor, then:
git add .
git commit -m "Resolved conflicts with main"

# 5. Push resolved feature branch
git push origin feature-branch

Now your PR should be ready to merge! ✅

📊 Git Workflow Diagram

Git Workflow

🎯 Quick Reference Cheat Sheet

Task	Command
Initialize repo	`git init`
Check status	`git status`
Stage all changes	`git add .`
Commit changes	`git commit -m "message"`
View history	`git log --all --graph`
Create branch	`git branch branch-name`
Switch branch	`git checkout branch-name`
Merge branch	`git merge branch-name`
Clone repo	`git clone <url>`
Push to remote	`git push origin main`
Pull from remote	`git pull origin main`

CAUTION!

Changing history (with --amend, reset, or --force) can have nasty side effects. If you need to change commits that already exist on GitHub, proceed with caution!

Credits: Omar Faruk

Technical

Git & GitHub: From Zero to Pro ​

📌 What is Git & GitHub? ​

🖥️ Command Line Basics ​

⚙️ Initial Configuration ​

📦 Creating Commits ​

Initialize a Repository ​

Stage Changes (Add to Staging Area) ​

Create a Commit ​

View Commit History ​

🔄 Understanding Git Areas ​

Moving Between Areas ​

⏪ Viewing Previous Commits ​

🔧 Restoring to a Previous Commit ​

🛠️ Other Useful Git Features ​

Create Shortcuts (Aliases) ​

Ignore Files ​

Remove Git from a Project ​

☁️ Uploading Code to GitHub ​

Link Local to Remote Repository ​

Configure GitHub Credentials ​

Push Code to GitHub ​

⬇️ Downloading Code from GitHub ​

Clone a Repository ​

Fetch and Pull Updates ​

🌿 Branching ​

Understanding HEAD with Branches ​

🔀 Merging Branches ​

⚠️ Merge Conflicts ​

What a Conflict Looks Like ​

How to Resolve ​

🚀 Feature Branch Workflow ​

Step 1: Create a Feature Branch ​

Step 2: Make Changes and Commit ​

Step 3: Push Feature Branch to GitHub ​

Step 4: Create a Pull Request ​

Step 5: Merge the Pull Request ​

Step 6: Update Local Repository ​

🔥 Handling Merge Conflicts in Feature Branches ​

Option 1: Resolve on GitHub ​

Option 2: Resolve Locally ​

📊 Git Workflow Diagram ​

🎯 Quick Reference Cheat Sheet ​

Git & GitHub: From Zero to Pro

📌 What is Git & GitHub?

🖥️ Command Line Basics

⚙️ Initial Configuration

📦 Creating Commits

Initialize a Repository

Stage Changes (Add to Staging Area)

Create a Commit

View Commit History

🔄 Understanding Git Areas

Moving Between Areas

⏪ Viewing Previous Commits

🔧 Restoring to a Previous Commit

🛠️ Other Useful Git Features

Create Shortcuts (Aliases)

Ignore Files

Remove Git from a Project

☁️ Uploading Code to GitHub

Link Local to Remote Repository

Configure GitHub Credentials

Push Code to GitHub

⬇️ Downloading Code from GitHub

Clone a Repository

Fetch and Pull Updates

🌿 Branching

Understanding HEAD with Branches

🔀 Merging Branches

⚠️ Merge Conflicts

What a Conflict Looks Like

How to Resolve

🚀 Feature Branch Workflow

Step 1: Create a Feature Branch

Step 2: Make Changes and Commit

Step 3: Push Feature Branch to GitHub

Step 4: Create a Pull Request

Step 5: Merge the Pull Request

Step 6: Update Local Repository

🔥 Handling Merge Conflicts in Feature Branches

Option 1: Resolve on GitHub

Option 2: Resolve Locally

📊 Git Workflow Diagram

🎯 Quick Reference Cheat Sheet