GIT107 - Handling Merge Conflicts

Merge conflicts are a normal part of working with Git, especially when collaborating on shared code.
A merge conflict occurs when Git cannot automatically combine changes between branches because the same part of a file was modified in two different ways.

Understanding how conflicts happen and how to fix them is an essential Git skill.

Why Merge Conflicts Happen

Merge conflicts usually occur when:

• Two branches modify the same line of code
• One branch deletes a file that another branch edits
• Two developers edit the same file simultaneously
• Automatic merge is not possible due to overlapping changes

Git stops the merge and asks for human intervention.

Creating a Merge Conflict (Example)

Imagine two branches: main and feature/update-title

On main, the file says:

title = "Homepage"

On feature/update-title, the file says:

title = "New Homepage Title"

When merging feature/update-title into main:

git checkout main
git merge feature/update-title

Git will detect conflicting edits on the same line and stop the merge.

What a Merge Conflict Looks Like

Git adds special markers to show the conflicting sections inside the file:

<<<<<<< HEAD
title = "Homepage"
======
title = "New Homepage Title"
>>>>>>> feature/update-title

Meaning of markers:

• HEAD block = your current branch
• After ====== = incoming changes
• After >>>>>>> = which branch the change came from

How to Resolve a Merge Conflict

Steps to fix the conflict:

1. Open the conflicted file
2. Decide which version to keep
3. Remove all conflict markers
4. Save the resolved file
5. Stage the file:

git add filename

6. Complete the merge:

git commit

Git now records a merge commit that includes your resolved changes.

Resolution Options

Depending on the situation, you may choose to:

• Keep your version
• Keep the incoming version
• Combine both changes
• Rewrite the section completely

Example combining both:

title = "Homepage - New Title"

Using Git Merge Tools

Git supports external merge tools for easier conflict resolution.

Set a mergetool globally:

git config --global merge.tool vimdiff

Run the merge tool:

git mergetool

Common tools:

• vimdiff
• kdiff3
• meld
• Beyond Compare

Viewing Conflict Status

List files with conflicts:

git status

Git displays:

both modified: filename

Aborting a Merge

If you want to cancel the merge and restore the previous state:

git merge --abort

Useful when the conflict is too complicated or the merge attempt was a mistake.

Summary

In this chapter, you learned:

• What merge conflicts are and why they happen
• How Git marks conflicted sections
• How to manually resolve conflicts
• How to stage and commit resolved files
• How to use Git mergetool
• How to abort a merge if necessary

Merge conflicts are completely normal and nothing to fear.
With practice, they become easy to understand and resolve efficiently.

Next, we will explore Git workflow models such as feature branching, Git Flow, and trunk-based development.