Branching — Create, Switch, Merge

# List all branches (* = current)
git branch
# * main
#   feature/user-auth

# Create a branch and switch to it (preferred modern syntax)
git switch -c feature/payment-gateway

# Older syntax (still works everywhere)
git checkout -b feature/payment-gateway

# Switch between branches
git switch main
git switch feature/payment-gateway

# Create branch from a specific commit or tag
git switch -c hotfix/login-crash origin/main
git switch -c release/v2.0 v1.9.0

# Delete a branch (safe — checks for unmerged work)
git branch -d feature/payment-gateway
git branch -D feature/payment-gateway  # force delete

//  FAST-FORWARD MERGE (no divergence)
//
//  Before:
//  main:    A ── B
//                â””── C ── D  ← feature
//
//  git switch main && git merge feature
//
//  After (pointer just moves forward, no merge commit):
//  main:    A ── B ── C ── D  ← main & feature

//  THREE-WAY MERGE (both branches have new commits)
//
//  Before:
//  main:    A ── B ── E       ← main moved forward
//                â””── C ── D  ← feature
//
//  After:
//  main:    A ── B ── E ── M  ← merge commit M
//                â””── C ── D ─┘

# Perform the merge
git switch main
git merge feature/payment-gateway

# Prevent fast-forward (always create a merge commit)
git merge --no-ff feature/payment-gateway

# Merge commit message appears in editor — describe the integration

# Git marks conflicts like this:
<<<<<<< HEAD (your branch — main)
function login(email, password) {
  if (!email || !password) throw new Error('Missing credentials')
=======
function login(email, password) {
  validateInput(email, password)  // refactored validation
>>>>>>> feature/payment-gateway

# 1. Edit the file to the correct final state:
function login(email, password) {
  if (!email || !password) throw new Error('Missing credentials')
  validateInput(email, password)
}

# 2. Stage the resolved file
git add src/auth.js

# 3. Complete the merge
git commit  # Git pre-fills the merge commit message

# Abort a merge if you need to start over
git merge --abort

# Use a visual merge tool
git mergetool  # opens configured tool (VSCode, vimdiff, etc.)