Fast Forward Merge in Git Explained with Examples

When working on new features, you often create separate branches in Git. At some point, you’ll want to bring your feature branch back into main. In this blog, we’ll learn branch merging, focusing on the fast forward merge, and also see how to list merged and unmerged branches.

Setting Up the Project

We start with a fresh project:

mkdir project3
cd project3
git init

Add a file and make the first commit:

echo "Hello World" > hello.txt
git add .
git commit -m "Initial commit"

Visualization shows one commit at this stage.

Creating a Feature Branch

Now we need to add a chat feature. For this, we create a new branch:

git switch -C feature/chat

We are now on the feature/chat branch. Add and commit files:

echo "Chat feature - step 1" > feature_chat.txt
git add feature_chat.txt
git commit -m "Add chat feature step 1"

echo "Chat feature - step 2" >> feature_chat.txt
git add feature_chat.txt
git commit -m "Add chat feature step 2"

At this point, feature/chat has multiple commits ahead of main.

Switching Back to Main

Check main:

git switch main
cat hello.txt
# Hello World

The main branch does not have the chat feature commits yet.

What is Fast Forward Merge?

A fast forward merge happens when the target branch (e.g., main) has not diverged. Git simply moves the main branch pointer forward to the latest commit of feature/chat.

Diagram Before Merge



Here, main points to the first commit, while feature/chat is ahead.




Performing Fast Forward Merge


On the main branch:


git merge feature/chat



Now no new commit is created. Git just advances the main pointer.


Diagram After Merge




Both main and feature/chat now point to the same commit. That’s a fast forward merge.




Listing Branches


See all branches:


git branch
# main
# feature/chat



List branches that are merged into main:


git branch --merged



List branches that are not merged:


git branch --no-merged



If you create a test branch without merging:


git branch test



Then after making a commit in test, you’ll see it under git branch --no-merged.




Summary


    

  • Fast forward merge simply moves the pointer of the target branch forward.
    • 

  • It only works if the target branch has not diverged.
    • 

  • Use git branch --merged to see merged branches.
    • 

  • Use git branch --no-merged to see unmerged branches.
    • 





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