Merging Branches

Combine changes from one branch into another using git merge.

Types of Merges

Fast-Forward Merge

When the target branch has no new commits:

Before:
main: A---B
           \
feature:    C---D

After (fast-forward):
main: A---B---C---D

Three-Way Merge

When both branches have new commits:

Before:
main:    A---B---E
              \
feature:       C---D

After:
main:    A---B---E---M (merge commit)
              \     /
feature:       C---D

Merging Branches

Basic Merge

# Switch to target branch
git checkout main

# Merge source branch
git merge feature

Merge Options

Option	Description
--no-ff	Force merge commit (no fast-forward)
--squash	Combine all commits into one
--abort	Cancel merge in progress

No Fast-Forward

git merge --no-ff feature

Creates a merge commit even if fast-forward is possible.

Squash Merge

git merge --squash feature
git commit -m "Add feature"

Combines all feature commits into one.

Merge Conflicts

Conflicts occur when the same lines were changed in both branches.

<<<<<<< HEAD
current branch code
=======
incoming branch code
>>>>>>> feature

To resolve:

1. Edit the file to fix conflicts
2. Remove conflict markers
3. git add <file>
4. git commit

Exercise: Merge a Branch

Create a feature branch, switch back to main, and merge: