Session 2 — Exercises: Merge, Conflict, and Pull Request

Last updated on 2026-03-03 | Edit this page

Overview

In this session you will work in pairs to practise merging, resolving conflicts, and using pull requests.

Time frame: approximately 75 minutes of hands-on work.

Pair setup: decide who is Person A and who is Person B. You will both work on Person A’s repository.

Task 1: Mergeable Changes (No Conflict)

Level 1 — Edit different parts of the same file

  1. Person A: add Person B as a collaborator on your repository:
    • Go to Settings → Collaborators → Add people and enter Person B’s GitHub username.
  2. Person B: accept the invitation (check your email or GitHub notifications), then clone Person A’s repository in GitHub Desktop.
  3. Both partners edit README.md at the same time, but in different sections:
    • Person A: add a “Hobbies” section at the top.
    • Person B: add a “Favourite Books” section at the bottom.
  4. Person A: commit and push first.
  5. Person B: fetch, pull, then commit and push.
Callout

Checkpoint 1

Both changes appear in README.md on GitHub. Git merged them automatically because they did not overlap.

Level 2 — Try with a new file

Repeat the exercise, but this time each person creates a new file:

  • Person A creates hobbies.md.
  • Person B creates books.md.

Commit, push, and pull. Both files should appear in the repository without conflict.

Level 3 — Multiple rounds

Do two more rounds of non-conflicting edits to build confidence and speed with the commit → push → pull → commit → push cycle.

Task 2: Create and Resolve a Merge Conflict

Level 1 — Intentional conflict

  1. Both partners open README.md.
  2. Both edit the same line (for example, change the first line of the “About Me” section to something different).
  3. Person A: commit and push.
  4. Person B: commit, then try to push — GitHub Desktop will tell you to pull first.
  5. Person B: pull. A merge conflict will appear.
Callout

Checkpoint 2

GitHub Desktop shows a conflict notification. The conflicted file contains markers like:

<<<<<<< HEAD
Person A's version of the line.
=======
Person B's version of the line.
>>>>>>> main

Level 2 — Resolve the conflict

  1. Open the conflicted file in your text editor.
  2. Decide which version to keep (or combine both).
  3. Remove the conflict markers (<<<<<<<, =======, >>>>>>>).
  4. Save the file.
  5. In GitHub Desktop, mark the conflict as resolved and commit.
  6. Push the result.
Callout

Checkpoint 3

The repository now has a merge commit in its history. Both partners can pull and see the resolved file.

BASH 

# After a conflicting pull
git status                # shows conflicted files
# ... edit the file to resolve ...
git add README.md
git commit -m "Resolve merge conflict in README"
git push

Level 3 — Document the conflict

Add a short paragraph to your README describing:

  • What caused the conflict?
  • How did you resolve it?
  • What would you do differently next time?

Task 3: Branch and Pull Request

Level 1 — Create a branch and commit

  1. In GitHub Desktop, click Current branch → New branch.
  2. Name it add-resources (or another descriptive name).
  3. Create a new file called resources.md with a few useful links related to your studies or interests.
  4. Commit with the message Add resources file.
  5. Click Publish branch to push it to GitHub.
Callout

Checkpoint 4

On GitHub, you can see the new branch in the branch dropdown. The file resources.md exists only on the add-resources branch, not on main.

Level 2 — Open a pull request

  1. GitHub Desktop shows a prompt Create Pull Request — click it.
  2. On GitHub, fill in a title and description for your PR.
  3. Click Create pull request.
  4. Ask your partner to review the PR:
    • Go to the Files changed tab.
    • Leave at least one comment.
    • Approve the PR.
Callout

Checkpoint 5

The pull request page shows the conversation, file changes, and an approval.

Level 3 — Merge the pull request

  1. On the PR page, click Merge pull request → Confirm merge.
  2. Switch back to main in GitHub Desktop and pull.
  3. Verify that resources.md now exists on main.
  4. (Optional) Delete the merged branch on GitHub when prompted.

BASH 

# Create and switch to a new branch
git checkout -b add-resources

# ... make changes and commit ...
git add resources.md
git commit -m "Add resources file"

# Push the branch
git push -u origin add-resources

# After merging the PR on GitHub, update local main
git checkout main
git pull

Summary

By the end of this session you should have: