Day 3: Branching and Merging

Why Branches Matter

Branches are Git’s killer feature. They allow you to diverge from the main development line, experiment freely, and merge changes back when ready. Think of branches as parallel universes for your code.

Branch Fundamentals

bash

# List all branches
git branch

# Create a new branch
git branch feature/user-authentication

# Switch to the new branch
git checkout feature/user-authentication
# Or create and switch in one command
git checkout -b feature/user-authentication

# Modern syntax (Git 2.23+)
git switch feature/user-authentication
git switch -c feature/new-feature

Real-World Branching Example

Let’s implement a user authentication system:

bash

# Start from main branch
git switch main

# Create feature branch
git switch -c feature/auth-system

# Create authentication files
cat > auth.py &lt;&lt; 'EOF'
class UserAuth:
    def __init__(self):
        self.users = {}
    
    def register(self, username, password):
        if username in self.users:
            return False
        self.users[username] = password
        return True
    
    def login(self, username, password):
        return self.users.get(username) == password
EOF

# Stage and commit
git add auth.py
git commit -m "Add basic user authentication system"

# Continue development
echo "from auth import UserAuth" >> main.py
git add main.py
git commit -m "Integrate auth system with main application"

Merging Strategies

Fast-Forward Merge: When target branch hasn’t diverged, Git simply moves the pointer forward.

bash

git switch main
git merge feature/auth-system

Three-Way Merge: When both branches have new commits, Git creates a merge commit.

bash

# This creates a merge commit
git merge feature/complex-feature --no-ff

Squash Merge: Combines all feature commits into a single commit on target branch.

bash

git merge feature/small-fixes --squash
git commit -m "Implement multiple small UI fixes"

Handling Merge Conflicts

Conflicts occur when the same lines are modified in different branches:

bash

# When merge conflict occurs
git status  # Shows conflicted files

# Edit conflicted files (look for conflict markers)
# &lt;&lt;&lt;&lt;&lt;&lt;&lt; HEAD
# Your changes
# =======
# Their changes
# >>>>>>> branch-name

# After resolving conflicts
git add conflicted-file.py
git commit  # Git provides default merge message

Hands-On Exercise: Create two branches that modify the same file differently. Practice resolving the merge conflict manually.

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