Lesson 8: Merging Branches

What You'll Learn

In this lesson, you'll learn how to merge branches - combining work from different branches back together. This is a crucial skill for managing features and collaborating with others.

What is Merging?

Merging combines the commit history from one branch into another. Typically, you:

1. Create a feature branch
2. Make commits on the feature branch
3. When ready, merge the feature branch into main

Part 1: Basic Merge Workflow

Step-by-Step Example

# 1. Start on main branch
git switch main

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

# 3. Make changes and commit
echo "<footer>© 2026</footer>" >> index.html
git add index.html
git commit -m "Add footer to homepage"

# 4. Switch back to main
git switch main

# 5. Merge the feature branch
git merge feature/add-footer

What happens:

• Git combines commits from both branches
• The footer change is now in the main branch
• Your main branch has the latest code

Part 2: Types of Merges

Fast-Forward Merge

$ git merge feature/new-header
Updating abc1234..def5678
Fast-forward
 header.html | 5 +++++
 1 file changed, 5 insertions(+)

Fast-forward: Git just moves the main pointer to catch up with the feature branch.

Three-Way Merge

$ git merge feature/new-sidebar
Merge made by the 'recursive' strategy.
 sidebar.html | 10 ++++++++++
 1 file changed, 10 insertions(+)

Three-way merge: Git creates a new merge commit that combines both branches.

Part 3: After Merging

Delete the Feature Branch

Once merged, the feature branch is no longer needed:

git branch -d feature/add-footer

Push to GitHub

git push origin main

Delete Remote Branch

git push origin --delete feature/add-footer

Part 4: Viewing Merge History

See Graphical Log

git log --oneline --graph --all

Output shows branches and merges visually:

*   abc1234 (HEAD -> main) Merge branch 'feature/add-footer'
|\
| * def5678 Add footer to homepage
|/
* ghi9012 Update README

Part 5: Best Practices for Merging

Part 6: Complete Workflow Example

# 1. Update main branch
git switch main
git pull

# 2. Create feature branch
git switch -c feature/contact-form

# 3. Work on feature (multiple commits)
# ... make changes ...
git add .
git commit -m "Add contact form HTML"

# ... more changes ...
git add .
git commit -m "Style contact form"

# 4. Update from main (good practice)
git switch main
git pull
git switch feature/contact-form
git merge main  # Merge main into feature

# 5. Ready to merge - switch to main
git switch main

# 6. Merge feature branch
git merge feature/contact-form

# 7. Push to GitHub
git push

# 8. Clean up
git branch -d feature/contact-form
git push origin --delete feature/contact-form

Practice Exercise

1. Create a new branch called feature/add-styles
2. Create a file called style.css with some CSS
3. Commit your changes
4. Switch back to main
5. Merge the feature branch
6. Delete the feature branch
7. Push to GitHub

git switch -c feature/add-styles
echo "body { margin: 0; }" > style.css
git add style.css
git commit -m "Add basic styles"
git switch main
git merge feature/add-styles
git branch -d feature/add-styles
git push

Summary

What's Next?

In the next lesson, you'll learn how to handle merge conflicts - what happens when Git can't automatically merge changes, and how to resolve them manually.