tomsej/pi-ext/pr-explain

PR Explain

Generate an accurate English explanation of one PR. Read the repository; never modify it.

Read the PR

Input: PR number or URL.

• Metadata: gh pr view <n> --json title,body,baseRefName,headRefOid,url.
• Changes and evidence: gh pr diff <n> and gh pr checks <n>.
• Fetch without checkout: git fetch origin pull/<n>/head; inspect files with git show FETCH_HEAD:<path>.
• Read callers and surrounding code, not only the diff.
• Treat PR claims as claims: confirm each with code, tests, or CI; mark unsupported claims ⚠️.

Write the explanation

Save ~/Workspace/specs/<project>/pr-<n>-<slug>/explanation.md; derive project, number, and slug—never guess them. Use these sections in order:

1. Background — optional newcomer context, then the specific problem.
2. Intuition — the core idea with small example data.
3. Change top to bottom — one causal architecture/code walkthrough.
4. Claims and evidence — claim, user-visible result, exact test/check evidence.
5. Try it yourself — disposable setup and observable checklist items - [ ].
6. Quiz — five useful multiple-choice questions.

Change map

Use closed <details> blocks: <code>PRINCIPLE</code> → <code>FLOW</code> → <code>STEP</code> → <code>KEPT</code> → <code>VERIFY</code>. Each <summary> must stand alone: label, short title, one-sentence conclusion. Inside STEP, include only important files: 🟡 <a href="<diff-url>"><code>MODIFIED</code></a> or 🟢 <a href="<diff-url>"><code>NEW</code></a>. Make the file name a permalink to exact HEAD lines: .../blob/<sha>/<path>#Lx-Ly. Show a short final-code snippet fenced with the language of the source file; link to the diff instead of pasting raw diff headers. Skip lockfiles, generated files, mechanical edits, and repeated prose.

Format

Write Markdown only. Use small mermaid diagrams with example data; no ASCII diagrams. Use exact symbol, test, and file names. Unknown facts are — or ⚠️, never inventions. Quiz answers must render inside raw HTML: <details><summary>Answer</summary><p><strong>B.</strong> Why it is right and the others are wrong.</p></details>. Print the absolute output path.

Share

Create and print the Plannotator URL; do not start a local server:

SHARE_URL="$(node -e 'const fs=require("node:fs"),z=require("node:zlib");const p=fs.readFileSync(process.argv[1],"utf8");console.log("https://share.plannotator.ai/#"+z.deflateRawSync(JSON.stringify({p,a:[]})).toString("base64url"))' "$EXPLANATION_PATH")"; printf 'Plannotator: %s\n' "$SHARE_URL"

The hash contains compressed, unencrypted content. Do not create it for sensitive PRs.