Teacher guide — Module 4 (2 periods)

Goal: students read history and diffs fluently and use them to answer who / when / what / why.

Timing: P1: hook 5, "Understand it" with the annotated diff on the board 10, unplugged 15, lab 1–2 (10). P2: lab 3–6 (25), Parsons 5, free-resource exercise 3 (5), exit 5. Materials: printed versions/v2.md and versions/v5.md (one pair each), red and green pens; for Tier 0 also log-sample.txt and versions/v3.md, versions/v4.md.

Facts about the practice repo you need

Commit (message)	What its diff does
1 Add working title	creates article.md with a title
2 Add better title and opening line	new title + first sentence (3 lines added, 1 removed)
3 Say where the festival is and what happens	changes the opening sentence
4 Add paragraph about food stalls and library fund	adds 2 lines
5 Add Class Eight momo paragraph (typo left in on purpose)	adds momo line and changes models → modals
6 Add closing sentence about the tastiest stall	extends the momo line and silently fixes modals → models

Commit ids depend on the time zone of the PC that built the repo, so read them from your own git log.

Common errors

• git log opens a pager and the student is stuck: press q to quit.
• Colour-blind students: also teach the + and - signs at the start of lines; the unplugged activity can use "circle" and "underline" instead of colours.
• Mixing up git diff (uncommitted) and git show (a commit). Keep the three-question table on the board.
• "git diff shows nothing" after staging: use git diff --staged.
• A changed word shows as a whole changed line — expected; Git compares lines.

Fallbacks

• Tier 0: print the two versions of article.md (commit 2 and commit 5) and the log from the practice repo; run the whole lesson on paper. The lab table (step 3) can be filled from the printed table above.
• One computer: project it; pairs answer on paper and call out predictions.

Differentiation

• Support: give the lab table with ids and messages already filled; students add authors, dates, sizes.
• Stretch: git log --since=2026-10-03, git log -p (every diff), git diff --word-diff.

Evidence to collect

The completed lab table and the hand-written diff (exercise 3).

Answer key

• Lab 1: commit 4, Add paragraph about food stalls and library fund.
• Lab 4: commit 6 fixed the typo; its message does not mention it → messages should describe every change, or the fix should have been its own commit.
• Exit 1: red/- removed, green/+ added. 2: author, date/time, message, parent commit (any two). 3: false.
• Parsons: git log --oneline list history · git show <id> commit changes · git diff uncommitted changes · git log --stat lines changed per commit.
• Free-resource 1: HEAD~1 means "one commit before the latest"; HEAD~2 two before.
• Free-resource 3: v3 → v4 adds a blank line and the food-stalls sentence (2 lines with +).

Extension quest

Find the commit where a word was misspelled and when it was fixed (commits 5 and 6).