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Git and GitHub

1. What is Git?

Git is a distributed version control system that tracks changes in source code and helps teams collaborate on projects.

  • Created by Linus Torvalds
  • CLI-based, fast, and efficient
  • Works offline

2. What is GitHub?

GitHub is a cloud-based hosting service for Git repositories. It adds collaboration features like pull requests, issues, and CI/CD.

3. Install and Configure Git

Install Git from: git website

Initial setup:

git config --global user.name "Your Name"
git config --global user.email "you@example.com"
````

Check config:

```bash
git config --list

4. Basic Commands

git init            # Initialize a new repo
git status          # Show file status
git add <file>      # Stage file
git commit -m "msg" # Commit staged changes
git log             # View commit history

Stage all files:

git add .

5. Working with GitHub

Create a Repository

  1. Create a new repo on GitHub (don't initialize with README)
  2. In terminal:
git remote add origin https://github.com/user/repo.git
git branch -M main
git push -u origin main

6. .gitignore

Use .gitignore to exclude files/folders from being tracked.

Example:

node_modules/
.env
.DS_Store

7. Cloning Repositories

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

8. Branching

git branch         # List branches
git branch dev     # Create branch
git switch dev     # Switch branch (or: git checkout dev)
git merge dev      # Merge dev into current branch

Delete a branch:

git branch -d dev

9. Handling Merge Conflicts

When two branches modify the same line:

<<<<<<< HEAD
your version
=======
incoming version
>>>>>>> dev

Resolve manually, then:

git add .
git commit

10. Undoing Changes

Discard unstaged changes:

git restore <file>

Unstage a file:

git reset <file>

Reset entire repo:

git reset --hard HEAD

Revert a commit (safe):

git revert <commit-hash>

11. Stashing Changes

Temporarily save work:

git stash
git stash list
git stash apply
git stash pop

12. Working with Remotes

git remote -v                # Show remotes
git remote add origin <url>  # Add remote
git push origin main         # Push to remote
git pull origin main         # Pull latest

13. Pull Requests (PRs)

  1. Push branch to GitHub
  2. Click "Compare & Pull Request"
  3. Add title, description, reviewers
  4. Merge after approval

14. Fork vs Clone

  • Fork: Your own copy of someone else’s repo (for contributing)

  • Clone: Local copy of any repo (for development)

15. Tags and Releases

git tag v1.0
git tag -a v1.1 -m "Version 1.1"
git push origin --tags

Use tags on GitHub to create releases.

16. Rebase (Advanced)

git rebase main         # Rebase current branch onto main
git rebase -i HEAD~3    # Interactive rebase last 3 commits

Squash commits by choosing s for all except the first.

17. Authentication Methods

HTTPS with Token:

git remote set-url origin https://<token>@github.com/user/repo.git

SSH:

  1. Generate key:
ssh-keygen -t ed25519 -C "you@example.com"

  1. Add public key to GitHub → Settings → SSH & GPG

  2. Test:

ssh -T git@github.com

18. Git Tools

  • GitHub Desktop – GUI for GitHub workflows
  • Sourcetree, GitKraken – Git GUI clients
  • GitLens (VS Code) – Git insights in editor

19. Git Hooks (Optional)

Automate actions on Git events:

Example: .git/hooks/pre-commit

#!/bin/sh
npm run lint

Make it executable:

chmod +x .git/hooks/pre-commit

20. Best Practices

  • Commit often with meaningful messages
  • Use .gitignore to avoid committing unwanted files
  • Use branches for features/fixes
  • Don’t commit secrets (use .env)
  • Resolve merge conflicts carefully
  • Keep pull requests small and focused
  • Never force push to main unless you know what you’re doing

Commit Message Format

Use present tense, short, descriptive messages:

git commit -m "Add contact form validation"

Prefix (optional): feat, fix, docs, refactor, test, etc.

Summary Cheatsheet

Command Description
git init Start new repository
git clone <url> Clone a repo
git status Show status
git add . Stage all changes
git commit -m "" Commit changes
git push origin main Push to GitHub
git pull origin main Pull latest from GitHub
git branch <name> Create new branch
git switch <branch> Switch branch
git merge <branch> Merge into current
git log Show commit history
git stash Save uncommitted work
git tag v1.0 Create version tag