Chapter 4 · Undo, and git — Learn AI by Building

Goes with Episode 4"How do I undo what Claude Code just did?". The video is being made. This page teaches the same steps, at your own pace.

In a hurry?Jump to the quick reference: every command and key in this chapter, what it does, and when to use it.

Every prompt, ready to copyThis chapter's prompts and commands, each with a Copy button. Type them yourself first; copy if you are stuck or behind.

Where you areDevPulse with a server, two views, an edit button and a CLAUDE.md, from chapter 3.

A big change you did not want

So far every change was small. Now ask for a big one, in four words.

Type this into Claude CodeGive DevPulse a modern makeover.

40 seconds later: a new logo, new colours, new shapes, new motion. A lot at once.

Left, before. Right, after. Say you do not like it. It is not ours any more.

The question for this chapter

How do you get your project back exactly as it was, and how do you never lose a version you liked?

First, see what changed

Before undoing, look. Claude Code has a command that shows every change.

Type this into Claude Code/diff

/diff: The diff panel shows git changes. The current directory isn't in a git repository. — It cannot. `/diff` needs **git**, and our project has none yet. Remember this line; we fix it below.

Rewind, and where it stops

We met rewind in chapter 3. Press Esc twice and pick the message before the makeover.

Rewind: Restore the code and/or conversation to the point before… Give DevPulse a modern makeover. 2 files changed +177 -2. — Rewind knows its own size: **2 files changed, +177 −2**. Even without git, it can count.

Confirm: The code will be restored +2 -177 in style.css and index.html. Options: Restore code and conversation, Restore conversation, Restore code, Summarize from here, Summarize up to here. Warning: Restored files go back whole, losing later changes by anyone. Bash changes to other files are not undone. — Choose **Restore code and conversation**. Read the warning at the bottom first: *Bash changes to other files are not undone.*

Now refresh the page.

Half back. The logo tile is gone. The glow and the pill tabs stayed.

Why? Look at how Claude worked. It changed the header with its edit tool. But it put most of the new style in with a shell command.

During the makeover: Running a PowerShell command that reads a scratchpad style.css and writes it into index.html. — The makeover went in partly through a **shell command**. Rewind tracks Claude's edit tool, not commands.

So rewind is a good undo for Claude's own edits. It is not a safety net for the whole project. I had a copy of the old index.html, so I put it back by hand. Without a copy, you would ask Claude to repair it, and hope.

That copy should not depend on luck. That is what git is for.

Keep every version with git

Git keeps a saved copy of your project each time you say "this works". Each saved copy is called a commit. You do not need to know the git commands yet. Ask Claude.

Type this into Claude Code, as one lineSet up git for this project. Keep data/tasks.json and Python caches out of git, and commit what we have.

Git is set up on branch main, and the first commit (897003a, Initial commit) has .gitignore, CLAUDE.md, index.html, server.py and test_server.py. .gitignore excludes data/tasks.json, __pycache__/ and *.pyc. I also ignored .claude/settings.local.json, which you didn't ask for. — The first commit, and a `.gitignore`: the list of files git must never save. Your tasks stay private. Note the honest line: *which you didn't ask for*.

Careful here

Git needs your name and email for every commit. If Claude says they are not set, run these two lines once, with your own details.

Type this in PowerShell or Terminal, oncegit config --global user.name "Your Name" git config --global user.email "you@example.com"

Commit with one command: a plugin

Committing well means a good message every time. Anthropic publishes a free plugin for that. Plugins add ready-made commands to Claude Code.

Type this into Claude Code, then search for commit-commands/plugin

The plugin manager, Discover tab, search box with commit-commands; result: commit-commands, Anthropic Directory, 178.5K installs, Streamline your git workflow with simple commands for committing. — The **Discover** tab. Press Enter on **commit-commands** to see its details.

Plugin details: commit-commands from claude-plugins-official, by Anthropic, a warning to trust a plugin before installing, and the options Install for you (user scope), Install for all collaborators on this repository (project scope), Install for you in this repo only (local scope). — Check who made it, read the warning, then choose **Install for you (user scope)**.

Now make one small change, then commit it.

Type these into Claude Code, one at a timeShow today's total time in the browser tab title, like "DevPulse - 2 h 50 min". /commit-commands:commit

Typing /commit shows three plugin commands: commit-commands:commit (Create a git commit), commit-commands:clean_gone, commit-commands:commit-push-pr. — Type `/commit` and the plugin's three commands appear. We use the first.

Committed 8ea96ee: Show today's total in tab title. Then ! git log --oneline lists 8ea96ee Show today's total in tab title, and 897003a Initial commit. — A short message, as chapter 3's memory asked. `! git log --oneline` shows our two commits. The grey line is only a suggestion.

What git costs

Git only keeps what you commit. A change you never committed is as unsafe as before. So commit each time something works, in small steps.

And a commit says the code runs. It does not say the code is right. In chapter 5 the streak looks right, passes our eyes, and is still wrong.

Quick reference

The prompts from this chapter, ready to copy: every prompt, chapter 4.

Command or key	What it does	Use it when
`/diff`	Shows what changed since the last commit	You want to see what Claude touched (needs git)
`Esc Esc`	Rewinds to an earlier message: code, conversation or both	You want to undo Claude's last steps
`Restore code and conversation`	Puts files and the chat back as they were	Both the change and the talk about it should go
`Set up git for this project …`	Claude runs git init, writes .gitignore and makes the first commit	Your project has no history yet
`/plugin`	Opens the plugin manager: discover, install, manage	You want a ready-made set of commands
`/commit-commands:commit`	Writes a commit message and commits your changes	A change is done and works
`! git log --oneline`	Lists your commits, newest first	You want to see your history

Your homework

Break it, then get it back with git

The goal: undo a change with git, not with rewind.

The steps: ask Claude to change the Add button to bright red. Do not commit. Then type: Throw away all changes since the last commit.

Guess first: will Claude ask before throwing work away?

One question for you: how often should you commit while building with Claude, and why?

References

Where each command and behaviour on this page comes from. Every screenshot is from our own recording on 29 Oct 2026, Claude Code 2.1.312.

Anthropic · Checkpointing Esc Esc rewinds code and conversation; changes made by shell commands are not tracked, so they are not undone. https://code.claude.com/docs/en/checkpointing
Anthropic · Discover and install plugins /plugin, the official marketplace claude-plugins-official, and install scopes. https://code.claude.com/docs/en/discover-plugins
Git · git-scm.com, the Git documentation What a commit, git log and .gitignore are. https://git-scm.com/doc
My own recording · 29 Oct 2026, Windows 11 Rewind undid the edit-tool changes but not the shell command, so half the makeover stayed.

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