Hi Product Hunt 👋 I'm Dai, the maker of diff-tour.

I also run WebTerm Learn, which launched here in August, and I talk with a lot of people who teach software engineering. One question comes up again and again: now that AI writes the code, what should engineers learn?

People rarely write code by hand anymore. AI often reviews it too, and software moves so fast that reading every line is hard. Still, I'm sure of one thing: understanding code matters as much as ever. And understanding code means learning how a senior engineer thinks. That is what lets you give AI the right instructions, notice what really matters in a problem, design well, and keep a project moving in the right direction.

So diff-tour teaches that thinking on real changes. Point it at a branch, and the AI coding CLI you already use writes a tour of the change. Then you step through it with → and ←:

What the change is for, and which files to read next, including ones that didn't change
What a senior engineer asks: What if this runs twice? Can it be rolled back? Would the tests fail if the code broke?
What must be fixed, what's only a nit, and what looks risky but is fine
The moments they'd stop and say "wait", asked as questions so you can guess before you see the answer

Getting started is just this: install with the one-line script in the README, then run it in any git repository:

cd your-repo
tour

The first run asks for a language and an AI CLI, with recommended choices already selected. Press Enter three times and the tour starts being written.

Things I cared about:

It's read-only. The AI gets a copy of the files git tracks and read-only tools, enforced by command-line flags, not only by the prompt
The code on screen is read from git at the right commit, never copied from the AI's reply
No server, no telemetry, MIT licensed. It runs on your own Claude Code, Codex, Gemini, OpenCode or Copilot plan

diff-tour keeps growing, and what you say today shapes what comes next. I'd love to hear: which part of reading a change do you wish someone had taught you? And if a tour got something wrong, tell me where.