Git and GitHub Cheatsheet

A Comprehensive Guide from Beginner to Advanced

Author

Md Shahed Fardous (Samy)

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This cheatsheet provides a comprehensive guide to Git and GitHub, ranging from beginner to advanced concepts. It includes practical examples and illustrations to help you understand and apply Git commands effectively.

Table of Contents

1. Beginner Level
   • Setting up Git
   • Basic Commands
   • Branch Operations
2. Intermediate Level
   • Advanced Commit Operations
   • Stashing
   • Remote Operations
   • Viewing History
3. Advanced Level
   • Rebasing
   • Submodules
   • Hooks
   • Advanced GitHub Features
   • Git Internals
4. Git Workflow Illustrations
5. Practical Scenario: Contributing to an Open Source Project

Beginner Level

Setting up Git

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

Basic Commands

• Initialize a new Git repository:

  mkdir my-project
  cd my-project
  git init

• Clone a repository from GitHub:

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

• Stage changes for commit:

  git add file.txt
  git add .  # Stage all changes

• Commit staged changes:

  git commit -m "Add initial project files"

• Push commits to remote repository:

  git push origin main

• Fetch and merge changes from remote repository:

  git pull origin main

Branch Operations

• List branches: git branch
• Create a new branch: git branch <name>
• Switch to a branch: git checkout <branch>
• Merge a branch into the current branch: git merge <branch>

Example workflow:

git branch feature-login
git checkout feature-login
# Make changes
git add .
git commit -m "Implement login functionality"
git checkout main
git merge feature-login

Intermediate Level

Advanced Commit Operations

• Modify the last commit:

  git commit --amend -m "Updated commit message"

• Create a new commit that undoes specified commit:

  git revert abc123  # Revert the commit with hash abc123

• Reset to a specific commit, discarding all changes:

  git reset --hard HEAD~1  # Reset to the commit before HEAD

Stashing

• Temporarily store modified, tracked files: git stash
• Apply stored stash content and remove it: git stash pop
• List all stashed changesets: git stash list

Example workflow:

# You're working on a feature but need to switch branches
git stash
git checkout other-branch
# Do some work
git checkout original-branch
git stash pop  # Reapply your stashed changes

Remote Operations

• Add a new remote repository:

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

• Download objects and refs from another repository:

  git fetch upstream

• Fetch and rebase instead of merging:

  git pull --rebase origin main

Viewing History

• View commit history:

  git log --oneline --graph --decorate

• Show who last modified each line of a file:

  git blame README.md

Advanced Level

Rebasing

• Reapply commits on top of another base:

  git checkout feature-branch
  git rebase main

• Interactive rebase for editing commits:

  git rebase -i HEAD~3  # Interactively rebase the last 3 commits

Submodules

• Add a new submodule:

  git submodule add https://github.com/username/library.git

• Initialize and update submodules:

  git clone https://github.com/username/project.git
  cd project
  git submodule update --init --recursive

Hooks

Create scripts in .git/hooks/ directory to automate Git actions Example (pre-commit hook):

#!/bin/sh
# .git/hooks/pre-commit
npm run lint

Advanced GitHub Features

• Pull Requests: Propose changes and collaborate
• GitHub Actions: Automate workflows
• GitHub Pages: Host websites directly from a GitHub repository

Git Internals

• Objects: blobs, trees, commits, and tags
• Refs: pointers to commit objects

Git Workflow Illustrations

Basic Workflow

graph LR
    A[Working Directory] -->|git add| B[Staging Area]
    B -->|git commit| C[Local Repository]
    C -->|git push| D[Remote Repository]
    D -->|git pull| A

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Branching and Merging

gitGraph
    commit
    branch feature
    checkout feature
    commit
    commit
    checkout main
    merge feature
    commit

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Rebasing

gitGraph
    commit
    branch feature
    commit
    commit
    checkout main
    commit
    checkout feature
    commit
    checkout main
    merge feature

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Practical Scenario: Contributing to an Open Source Project

1. Fork the repository on GitHub
2. Clone your fork:

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

3. Set up upstream remote:

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

4. Create a feature branch:

   git checkout -b feature-name

5. Make changes and commit:

   git add .
   git commit -m "Implement new feature"

6. Push to your fork:

   git push origin feature-name

7. Create a pull request on GitHub
8. Update your pull request (if requested):

   git add .
   git commit -m "Address review comments"
   git push origin feature-name

9. Sync your fork with upstream:

   git fetch upstream
   git checkout main
   git merge upstream/main
   git push origin main

This workflow demonstrates how to contribute to an open-source project using Git and GitHub, incorporating forking, branching, and pull requests.

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© 2024 Md Shahed Fardous (Samy). All rights reserved.

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