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📌 1️⃣ What is Git?

Git is a distributed version control system used to track code changes and collaborate.

  • Created by Linus Torvalds
  • Official site: Git
  • Popular hosting: GitHub, GitLab, Bitbucket

📌 2️⃣ Installation

Windows

Download from git-scm.com

Ubuntu

sudo apt update
sudo apt install git -y

Verify

git --version

📌 3️⃣ Initial Setup (VERY IMPORTANT)

git config --global user.name "YuvaDevOps"
git config --global user.email "yuvaraj.k@raidenlabs.io"

Check:

git config --list

📌 4️⃣ Core Git Concepts

Concept Meaning
Working Directory Your project files
Staging Area Prepared changes
Repository (.git) Git database
Commit Snapshot
Branch Separate line of development
Remote Cloud repo

📌 5️⃣ Basic Workflow (Daily Use)

Step 1: Initialize Repo

git init

Step 2: Add Files

git add .

Step 3: Commit

git commit -m "Initial commit"

Step 4: Check Status

git status

Step 5: View History

git log --oneline --graph

📌 6️⃣ Connect to Remote (GitHub Example)

git remote add origin https://github.com/username/repo.git
git branch -M main
git push -u origin main

📌 7️⃣ Branching (Very Important for Real Projects)

Create Branch

git checkout -b feature/login

Switch Branch

git checkout main

Merge Branch

git merge feature/login

📌 8️⃣ Merge Conflicts (Most Common Interview Question)

When two developers change same lines.

Resolve:

  1. Open file
  2. Fix conflict
  3. Add again
git add .
git commit

📌 9️⃣ Pull & Fetch

git pull origin main

Better way:

git fetch
git merge origin/main

📌 🔟 Rebase (Advanced)

Rebase keeps history clean.

git checkout feature
git rebase main

⚠️ Never rebase shared branch.

📌 11️⃣ Stash (Save Work Temporarily)

git stash
git stash list
git stash apply
git stash pop

📌 12️⃣ Undo Scenarios (VERY IMPORTANT)

Undo last commit (keep changes)

git reset --soft HEAD~1

Undo and delete changes

git reset --hard HEAD~1

Restore file

git restore file.txt

📌 13️⃣ Cherry Pick

Take commit from another branch:

git cherry-pick <commit-id>

📌 14️⃣ Tagging (Release Versioning)

git tag v1.0
git push origin v1.0

📌 15️⃣ Git Workflow Models

1️⃣ Git Flow

  • main
  • develop
  • feature/*
  • release/*
  • hotfix/*

2️⃣ GitHub Flow

  • main
  • feature branches

Most modern teams use GitHub Flow.

📌 16️⃣ Working with Forks

  1. Fork repo
  2. Clone fork
  3. Add upstream
git remote add upstream https://github.com/original/repo.git
git fetch upstream
git merge upstream/main

📌 17️⃣ Submodules

Add another repo inside project:

git submodule add https://github.com/user/lib.git

Update:

git submodule update --init --recursive

📌 18️⃣ Large Files (Git LFS)

git lfs install
git lfs track "*.zip"

📌 19️⃣ Fixing Mistakes & Recovery

Deleted branch?

git reflog
git checkout -b recovered <commit-id>

Remove remote branch

git push origin --delete feature/login

📌 20️⃣ DevOps + CI/CD Usage

In GitHub Actions

- uses: actions/checkout@v4

Docker build from repo

docker build -t app:v1 .

Tag version automatically

git tag v1.1
git push origin v1.1

📌 21️⃣ Real World Scenarios (Important)

🔥 Scenario 1: Force push?

git push --force

⚠️ Dangerous. Avoid on shared branches.

🔥 Scenario 2: Remove sensitive file

git rm --cached .env

Add to .gitignore

🔥 Scenario 3: Rename branch

git branch -m old-name new-name

🔥 Scenario 4: Squash commits

git rebase -i HEAD~3

📌 22️⃣ .gitignore Example

node_modules/
.env
dist/
*.log

📌 23️⃣ Git Best Practices

✔ Small commits ✔ Meaningful messages ✔ Pull before push ✔ Never commit secrets ✔ Use feature branches ✔ Protect main branch

📌 24️⃣ Interview Questions

  • Difference between merge and rebase?
  • What is detached HEAD?
  • What is git reflog?
  • Explain git stash internally?
  • How git stores objects? (Blob, Tree, Commit)

📌 25️⃣ Internal Architecture (Deep Level)

Git stores objects in:

.git/objects

Types:

  • Blob
  • Tree
  • Commit
  • Tag

Git uses SHA-1 hash.

📌 26️⃣ Advanced Commands

git bisect
git blame
git clean -fd
git revert
git worktree

📌 27️⃣ Enterprise Workflow (DevOps Engineer Level)

For your DevOps background:

  1. Feature branch
  2. PR
  3. Code review
  4. CI pipeline
  5. Merge
  6. Auto tag
  7. Docker build
  8. Deploy via Terraform

📌 28️⃣ Complete Real Project Flow

git clone repo
git checkout -b feature/payment
# code
git add .
git commit -m "Add payment API"
git push origin feature/payment
# create PR
# merge after review
git checkout main
git pull

🎯 Final Summary

If you master:

  • Branching
  • Rebase
  • Conflict resolution
  • Reflog recovery
  • CI integration
  • Tagging strategy
  • Git internals

👉 You are production-ready Git user