Git Branch Merge

What is Merging in Git?

Merging in Git means combining the changes from one branch into another.

This is how you bring your work together after working separately on different features or bug fixes.

Common git merge Options

• git merge - Merge a branch into your current branch
• git merge --no-ff - Always create a merge commit
• git merge --squash - Combine changes into a single commit
• git merge --abort - Abort a merge in progress

Merging Branches (git merge)

To combine the changes from one branch into another, use git merge.

Usually, you first switch to the branch you want to merge into (often main or master), then run the merge command with the branch name you want to combine in.

First, we need to change to the main branch:

git checkout main
Switched to branch 'main'

Now we merge the current branch (main) with emergency-fix:

git merge emergency-fix
Updating f938b79..e7e2d06
Fast-forward
 index.html | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Since the emergency-fix branch came directly from main, and no other changes had been made to main while we were working, Git sees this as a continuation of main.

So it can "Fast-forward", just pointing both main and emergency-fix to the same commit.

As main and emergency-fix are essentially the same now, we can delete emergency-fix, as it is no longer needed:

git branch -d emergency-fix
Deleted branch emergency-fix (was e7e2d06).

Best Practices for Merging Branches

Practical Examples

Non-Fast-Forward Merge (git merge --no-ff)

By default, if your branch can be merged with a fast-forward (no new commits on the base), Git just moves the branch pointer forward.

If you want to always create a merge commit (to keep history clearer), use git merge --no-ff branchname.

git merge --no-ff feature-branch
Merge made by the 'ort' strategy.
 index.html | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Squash Merge (git merge --squash)

If you want to combine all the changes from a branch into a single commit (instead of keeping every commit), use git merge --squash branchname.

This is useful for cleaning up commit history before merging.

git merge --squash feature-branch
Automatic merge went well; stopped before committing as requested
Squash commit -- not updating HEAD

Aborting a Merge (git merge --abort)

If you run into trouble during a merge (like a conflict you don't want to resolve), you can cancel the merge and go back to how things were before with git merge --abort.

git merge --abort

What is a Merge Conflict?

A merge conflict happens when changes in two branches touch the same part of a file and Git doesn't know which version to keep.

Think of it like two people editing the same sentence in a document in different ways. Git needs your help to decide which version to use.

How to Resolve a Merge Conflict

Git will mark the conflict in your file.

You need to open the file, look for lines like <<<<<<< HEAD and =======, and decide what the final version should be.

Then, stage and commit your changes.

Troubleshooting & Tips

• If you want to cancel a merge, use git merge --abort.
• Always commit or stash your changes before starting a merge.
• Read the conflict markers carefully and remove them after you've resolved the issue.
• Use git status to see what files need your attention.
• If you're unsure, ask a teammate or look up the error message.

Merge Conflict Example

Now we can move over to hello-world-images from last chapter, and keep working.

Add another image file (img_hello_git.jpg) and change index.html, so it shows it:

git checkout hello-world-images
Switched to branch 'hello-world-images'

Now, we are done with our work here and can stage and commit for this branch:

git add --all
git commit -m "added new image"
[hello-world-images ff63d40] added new image
 2 files changed, 1 insertion(+)
 create mode 100644 img_hello_git.jpg

We see that index.html has been changed in both branches.

Now we are ready to merge hello-world-images into main.

But what will happen to the changes we recently made in main?

git checkout main
Switched to branch 'main'
git merge hello-world-images
Auto-merging index.html
CONFLICT (content): Merge conflict in index.html
Automatic merge failed; fix conflicts and then commit the result.

The merge failed, as there is a conflict between the versions for index.html.

Let us check the status:

git status
On branch main
You have unmerged paths.
  (fix conflicts and run "git commit")
  (use "git merge --abort" to abort the merge)

Changes to be committed:
        new file:   img_hello_git.jpg
        new file:   img_hello_world.jpg

Unmerged paths:
  (use "git add <file>..." to mark resolution)
        both modified:   index.html

This confirms there is a conflict in index.html, but the image files are ready and staged to be committed.

So we need to fix that conflict. Open the file in our editor:

We can see the differences between the versions and edit it like we want:

Now we can stage index.html and check the status:

git add index.html
git status
On branch main
All conflicts fixed but you are still merging.
  (use "git commit" to conclude merge)

Changes to be committed:
        new file:   img_hello_git.jpg
        new file:   img_hello_world.jpg
        modified:   index.html

The conflict has been fixed, and we can use commit to conclude the merge:

git commit -m "merged with hello-world-images after fixing conflicts"
[main 00f1c9e] merged with hello-world-images after fixing conflicts

And delete the hello-world-images branch:

git branch -d hello-world-images
Deleted branch hello-world-images (was ff63d40).

Now you have a better understanding of how branches and merging work.

Time to start working with a remote repository!