Lesson 1: The Negotiator (Merge Conflicts)

What happens when two people edit the same line of the same file? Git can't decide which version to keep. It raises its hands and says: "You figure it out." This is a merge conflict.

When Do Conflicts Happen?

Conflicts occur when:

• Two branches modify the same line of the same file.
• One branch deletes a file that the other modified.
• Both branches add a file with the same name.

What a Conflict Looks Like

When Git encounters a conflict, it marks the file with special conflict markers:

<<<<<<< HEAD
const port = 3000;
=======
const port = 8080;
>>>>>>> feature/new-port

• <<<<<<< HEAD — Your current branch's version.
• ======= — The divider between the two versions.
• >>>>>>> feature/new-port — The incoming branch's version.

How to Resolve a Conflict

Step 1: Identify the conflicting files

git status
# You'll see: "both modified: app.config"

Step 2: Open the file and decide

Edit the file to keep the version you want. Remove the conflict markers:

// BEFORE (with conflict markers):
<<<<<<< HEAD
const port = 3000;
=======
const port = 8080;
>>>>>>> feature/new-port

// AFTER (your decision):
const port = 8080;

Step 3: Mark as resolved

git add app.config

Step 4: Complete the merge

git commit -m "Resolve port conflict, use 8080"

Tips for Resolving Conflicts

• 🧠 Understand both sides before choosing.
• 📞 Talk to the other developer if you're unsure.
• ✅ Run tests after resolving to make sure nothing broke.
• 🔍 Use git diff to double-check your resolution.

Mission Objective

Experience your first merge conflict:

1. Set the stage: Create a branch with git checkout -b conflict-demo.
2. See the conflict: Run cat app.config to view the conflict markers.
3. Resolve it: After editing, mark the file as resolved with git add app.config.

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Real-World Wisdom

Senior engineers say: "The best way to handle merge conflicts is to prevent them." Keep branches short-lived, merge frequently, and communicate with your team about which files you're editing.