Git Branches¶

1. What are Branches?¶

Branches are independent workspaces. You can develop new features or fix bugs without affecting the main code.

         feature-login
              │
              ▼
        ┌───(B)───(C)
        │
(1)───(2)───(3)───(4)   main
              │
              ▼
        └───(X)───(Y)
              │
              ▼
         bugfix-header

Why Use Branches?¶

Safe Experimentation: Test new features without damaging main code
Parallel Work: Develop multiple features simultaneously
Organized Management: Separate work by feature or bug
Easy Collaboration: Each person works on their branch, then merges

2. Basic Branch Commands¶

List Branches¶

# List local branches
git branch

# Include remote branches
git branch -a

# Show detailed branch information
git branch -v

Create Branch¶

# Create branch (without switching)
git branch branch-name

# Create branch + switch
git checkout -b branch-name

# Git 2.23+ recommended method
git switch -c branch-name

Switch Branch¶

# Traditional method
git checkout branch-name

# Git 2.23+ recommended method
git switch branch-name

Delete Branch¶

# Delete merged branch
git branch -d branch-name

# Force delete (even if not merged)
git branch -D branch-name

Rename Branch¶

# Rename current branch
git branch -m new-name

# Rename specific branch
git branch -m old-name new-name

3. Merging Branches¶

Merge a completed branch into another branch.

Basic Merge¶

# 1. Switch to main branch
git switch main

# 2. Merge feature branch into main
git merge feature-branch

Types of Merges¶

Fast-forward Merge¶

When there are no changes to main after branching:

Before:
main:    (1)───(2)
                └───(A)───(B)  feature

After:
main:    (1)───(2)───(A)───(B)
                              feature (deleted)

git switch main
git merge feature
# Fast-forward message displayed

3-Way Merge¶

When both branches have changes:

Before:
              (A)───(B)  feature
             /
main:  (1)───(2)───(3)───(4)

After:
              (A)───(B)
             /         \
main:  (1)───(2)───(3)───(4)───(M)  Merge commit

git switch main
git merge feature
# Merge commit created

4. Conflict Resolution¶

Conflicts occur when the same part of the same file is modified.

Conflict Markers in File¶

<<<<<<< HEAD
Content modified in main branch
=======
Content modified in feature branch
>>>>>>> feature-branch

Conflict Resolution Process¶

# 1. Check conflict
git status
# Output: both modified: conflict-file.txt

# 2. Open file and resolve conflict
# Edit from <<<<<<< HEAD to >>>>>>>

# 3. Stage after resolution
git add conflict-file.txt

# 4. Complete merge
git commit -m "merge: merge feature-branch, resolve conflicts"

Conflict Resolution Example¶

Before resolution:

<<<<<<< HEAD
console.log("Hello from main");
=======
console.log("Hello from feature");
>>>>>>> feature-branch

After resolution:

console.log("Hello from main");
console.log("Hello from feature");

Abort Merge¶

# Abort merge during conflict
git merge --abort

5. Branch Strategies¶

Git Flow¶

main ─────────────────────────────────────────▶ Production
  │
  └─ develop ─────────────────────────────────▶ Development
       │
       ├─ feature/login ──────────────────────▶ Feature development
       │
       ├─ feature/signup ─────────────────────▶ Feature development
       │
       └─ release/1.0 ────────────────────────▶ Release preparation

Branch Naming Conventions¶

Prefix	Purpose	Example
`feature/`	New feature development	`feature/login`
`bugfix/`	Bug fix	`bugfix/header-crash`
`hotfix/`	Urgent fix	`hotfix/security-patch`
`release/`	Release preparation	`release/1.0.0`

Practice Example: Complete Branch Workflow¶

# 1. Prepare project
mkdir branch-practice
cd branch-practice
git init
echo "# Main Project" > README.md
git add .
git commit -m "initial commit"

# 2. Create and switch to feature branch
git switch -c feature/greeting

# 3. Work on feature
echo "function greet() { console.log('Hello!'); }" > greet.js
git add .
git commit -m "feat: add greeting function"

echo "function bye() { console.log('Goodbye!'); }" >> greet.js
git add .
git commit -m "feat: add bye function"

# 4. Check branch status
git log --oneline --all --graph

# 5. Switch to main and merge
git switch main
git merge feature/greeting -m "merge: merge greeting feature"

# 6. Delete branch after merge
git branch -d feature/greeting

# 7. Check final history
git log --oneline --graph

Conflict Practice¶

# 1. Create branch
git switch -c feature/update

# 2. Modify README in feature
echo "Updated by feature" >> README.md
git add .
git commit -m "feat: update README"

# 3. Switch to main and modify same file
git switch main
echo "Updated by main" >> README.md
git add .
git commit -m "docs: update README"

# 4. Attempt merge - conflict occurs!
git merge feature/update
# CONFLICT message displayed

# 5. Open file, resolve conflict, then
git add README.md
git commit -m "merge: merge feature/update, resolve conflicts"

Command Summary¶

Command	Description
`git branch`	List branches
`git branch name`	Create branch
`git switch name`	Switch branch
`git switch -c name`	Create + switch
`git branch -d name`	Delete branch
`git merge branch`	Merge branch
`git merge --abort`	Abort merge
`git log --oneline --graph --all`	Branch graph

Next Steps¶

Let's learn about remote repositories and collaboration in 04_GitHub_Getting_Started.md!