Git Level 1 — Branching & Merging

01

WHY DO BRANCHES EXIST?

The Problem

Imagine you're building a feature but your code breaks halfway through. If everything is on main, your broken code is now live. Branches let you work in a safe sandbox — completely isolated from the rest of the project until you're ready.

Think of it like this

Your project is a book. main is the published version. A branch is like a personal notepad where you draft a new chapter. Once the chapter is good, you copy it into the book (merge). If you hate it, just throw the notepad away — the book is untouched.

💡 CONVENTION: Most teams use main (or master) as the stable production branch. New work always happens on feature branches, never directly on main.

02

THE 6 COMMANDS YOU NEED

Command	What it does
git branch	List all branches. The one with `*` is your current branch.
git branch <name>	Create a new branch. Doesn't switch to it yet.
git checkout <name>	Switch to an existing branch.
git checkout -b <name> shortcut	Create AND switch in one command. You'll use this 90% of the time.
git merge <name>	Merge the named branch INTO your current branch. Always switch to the target branch first.
git branch -d <name>	Delete a branch after merging. Use `-D` to force delete.

REAL WORKFLOW EXAMPLE

$ git checkout -b feature/dark-mode
Switched to a new branch 'feature/dark-mode'
 
# ... make your changes, then commit ...
$ git add .
$ git commit -m "feat: add dark mode toggle"
 
# Switch back to main and merge
$ git checkout main
$ git merge feature/dark-mode
Updating 3f2a1b..9c4d2e
Fast-forward
 
# Clean up the branch
$ git branch -d feature/dark-mode
Deleted branch feature/dark-mode (was 9c4d2e)

⚠️ MERGE RULE: You merge INTO the branch you're currently on. To bring feature into main, first checkout main, then merge feature.

03

INTERACTIVE TERMINAL LIVE

Try the commands yourself! This simulator mimics a real Git repo. Type commands below and see what happens.

Git simulator initialized. You have a repo with 2 commits on main.

Try: git branch, git checkout -b dev, git merge dev

─────────────────────────────────────────────

main $

QUICK COMMANDS:

04

KNOWLEDGE CHECK — 5 QUESTIONS

Q1. You want to create a new branch called feature/login AND immediately switch to it. Which command do you use?

Q2. You're on branch feature/login and you want to merge your work into main. What's the correct order of commands?

Q3. After merging feature/login into main, you want to delete the feature branch. Which command is safe to use?

Q4. You run git branch and see:

* main
  dev
  feature/login

Which branch are you currently on?

Q5. What does the -b flag stand for in git checkout -b?

05

HANDS-ON CHALLENGE — USE YOUR STATLAB

Now use what you learned on the real StatLab project you built today. Open your terminal, navigate to your project folder, and follow these steps:

Mission: Branch Like a Pro

Initialize git if not done: git init && git add . && git commit -m "initial commit"
Create and switch to a dev branch: git checkout -b dev
From dev, create a feature branch: git checkout -b feature/csv-upload
Open index.html, add a comment /* CSV upload coming soon */ anywhere
Stage and commit: git add . && git commit -m "feat: csv upload placeholder"
Switch back to dev: git checkout dev
Merge your feature: git merge feature/csv-upload
Delete the feature branch: git branch -d feature/csv-upload
Run git log --oneline and verify all commits are there
Push everything to GitHub: git push origin main && git push origin dev

✅ SUCCESS CHECK: Run git branch — you should only see main and dev. The feature branch should be gone. Run git log --oneline to see a clean history.