Lesson 3

🎯 Goal

Use branches: switch between them, push one, merge one, and learn the Pull First rule.

A branch is your own copy of the project where you can try things without touching anyone else’s work. nonRobot-module-2 is our shared starting point. Your own branch is training-yourname, the one you made in Lesson 2.

⚠️ The Pull First Rule

You MUST pull before you start coding. Every time.

While you were away, someone may have fixed or updated something. If you start coding on old code, your work is built on a stale copy and things break later.

Do this at the start of every coding session:

1. Click the branch name (top-left of the window, or bottom-right on older versions) and under Local choose nonRobot-module-2 → Checkout.
2. Click Git → Update Project… (or press Ctrl + T, Mac Cmd + T). If it asks Merge or Rebase, choose Merge. Click OK. (You just pulled!)
3. Switch back to your own branch, training-yourname.
4. Click the branch name, click nonRobot-module-2 in the list, and choose Merge ‘nonRobot-module-2’ into ‘training-yourname’.

Now you’re ready to code.

Why step 4? Pulling only updates nonRobot-module-2. Your own branch is a separate copy, so it doesn’t update by itself until you merge.

Task 1: Where am I?

1. Click the branch name. A list pops up with Local and Remote sections.
2. Look at both sections. In your doc, guess what the difference is.

✅ Checkpoint: you can find training-yourname and nonRobot-module-2 in the list.

Task 2: Pull first (do it now)

Follow The Pull First Rule above, all four steps.

✅ Checkpoint: you ended on training-yourname, and the merge in step 4 finished. Write in your doc what the pull in step 2 said (it’s often “All files are up-to-date”, and that’s fine).

If Git ever says CONFLICT: don’t panic, and don’t click anything. Two people changed the same line and Git needs a human to choose. Stop and ask David.

Task 3: Watch a file disappear

1. On training-yourname, open the Project panel and go to lib → Training.
2. Right-click Training → New → File, and make yourname-demo.txt with one line of text. Click Add if it asks about Git.
3. Open the Commit window, check your file, write a message, and click Commit.
4. Switch to nonRobot-module-2 (branch name → pick it → Checkout).
5. Look in lib/Training now. Where did your file go?
6. Switch back to training-yourname and watch it return.

✅ Checkpoint: you can explain, in one sentence, why the file disappeared. (It isn’t deleted. It only lives on your branch.)

Task 4: Push your branch

1. Git → Push… (Ctrl + Shift + K, Mac Cmd + Shift + K).
2. Click Push.

✅ Checkpoint: open feds-central on GitHub, pick training-yourname in the branch dropdown, and find yourname-demo.txt in lib/Training.

Task 5: Merge

Merging means combining one branch into another. You always stand on the branch that receives the changes. (You already did this in step 4 of the Pull First Rule. Now you’ll do it on purpose.)

1. While on training-yourname, make a new branch from it: branch name → New Branch… → training-yourname-extra.
2. On training-yourname-extra, make a file lib/Training/yourname-extra.txt and commit it.
3. Switch back to training-yourname. Look in lib/Training. Is yourname-extra.txt there?
4. Click the branch name, click training-yourname-extra in the list, and choose Merge ‘training-yourname-extra’ into ‘training-yourname’.
5. Look in lib/Training again.

✅ Checkpoint: yourname-extra.txt was missing at step 3 and there at step 5.

Cheat sheet

To complete this lesson

Paste into this lesson’s tab in your training doc (text only):

1. Your branch name or link (training-yourname)
2. Your guess about Local vs Remote (Task 1), and what it said when you pulled (Task 2)
3. Two sentences: what’s the difference between push and pull?