Skip to main content

🚩 Checkpoint 4: Break It and Recover

Everyone hits merge conflicts and bad commits. The difference between a beginner and a pro is that the pro is not scared of them. In this checkpoint you will cause a conflict on purpose in your own repo, fix it, then practice undoing a mistake safely.

Before you start

You need your repo from Checkpoint 3, plus the Merge Conflicts and Undo Mistakes lessons. Start on an up-to-date main: git switch main && git pull.

Part A — Create and resolve a conflict​

Step 1 — Add a notes file on main​

mkdir notes
echo "# Findings" > notes/findings.md
echo "" >> notes/findings.md
echo "Top category: Electronics" >> notes/findings.md
git add notes/findings.md
git commit -m "Add findings notes"

Step 2 — Change the same line on a branch​

git switch -c update-findings
echo "# Findings" > notes/findings.md
echo "" >> notes/findings.md
echo "Top category: Home & Garden" >> notes/findings.md
git add notes/findings.md
git commit -m "Update top category to Home & Garden"

Step 3 — Change that line differently on main​

git switch main
echo "# Findings" > notes/findings.md
echo "" >> notes/findings.md
echo "Top category: Books" >> notes/findings.md
git add notes/findings.md
git commit -m "Update top category to Books"

Now main and update-findings disagree about the same line. That is a conflict waiting to happen.

Step 4 — Trigger the conflict​

git merge update-findings

Git stops:

CONFLICT (content): Merge conflict in notes/findings.md
Automatic merge failed; fix conflicts and then commit the result.

Step 5 — Resolve it​

Open notes/findings.md. You will see the conflict markers:

# Findings

<<<<<<< HEAD
Top category: Books
=======
Top category: Home & Garden
>>>>>>> update-findings

Edit the file to the version you want and delete all three marker lines. For example:

# Findings

Top category: Books

Then complete the merge:

git add notes/findings.md
git commit

Save the editor that opens, and the merge is done. You survived your first conflict.

git branch -d update-findings

Part B — Undo a bad commit safely​

Step 6 — Make a "mistake"​

echo "DELETE FROM sales;  -- oops, do not run this" >> notes/findings.md
git add notes/findings.md
git commit -m "Add scary note"
git push

You pushed it, so others might have it. The safe undo is revert, not reset.

Step 7 — Revert it​

git revert HEAD

Save the editor. Git creates a new commit that undoes the bad one, keeping a clean, honest history. Push the fix:

git push

Look at notes/findings.md — the scary line is gone, and git log --oneline shows both the bad commit and the revert that cancelled it.

If something goes wrong​

SituationFix
Conflict feels overwhelmingBail out with git merge --abort and try Step 4 again
You deleted a marker line but left content wrongEdit the file again; nothing is committed until you git add + git commit
You used git reset --hard and lost a commitRun git reflog, find the commit, git reset --hard <hash> to bring it back
This is the whole point of Git

You just intentionally broke things and recovered every time. That safety net is why teams trust Git. Nothing you did here can be permanently lost.

✅ Checkpoint complete​

  • You created a merge conflict and resolved it
  • notes/findings.md exists with no conflict markers
  • You reverted a pushed commit with git revert
  • Your changes are pushed to GitHub

One more checkpoint to go: polishing the repo into something you would actually show an employer.

Donate to this project