Update PR Description

Read the current PR description and branch changes, then produce an updated description that accurately reflects what is on the branch. Always edit in-place — never recreate the PR.

Process

Phase 0: Verify GitHub CLI

gh auth status

Phase 1: Read Current PR State

gh pr view --json number,title,body,baseRefName,headRefName

Extract: PR number, existing body (may be empty), base branch, head branch.

NEVER hardcode main as base branch. Always read baseRefName from the PR.

Phase 2: Analyze Branch Changes

BASE=$(gh pr view --json baseRefName -q .baseRefName)
HEAD=$(gh pr view --json headRefName -q .headRefName)

git log --oneline "$BASE".."$HEAD"        # Commit history → Motivation
git diff --stat "$BASE".."$HEAD"          # File stats → Technical Details
git diff --name-only "$BASE".."$HEAD"     # File list → Test Plan

Phase 3: Decide How to Handle Existing Description

Do NOT discard user-written Motivation — it captures domain context the code cannot express.

Phase 4: Draft the Description

## Motivation
<Why this change — problem being solved, user need, or context>

## Technical Details
<Key implementation decisions, trade-offs, architecture changes>

## Test Plan
- [ ] <how this was tested>
- [ ] <edge cases verified>

Reference actual commits, files, and decisions — never use generic filler text.

Do NOT wrap prose at 80 characters. Write each paragraph as a single continuous line. Hard line breaks inside sentences make the rendered GitHub description look broken. Only break lines at natural paragraph boundaries (blank line between sections).

Phase 5: Show Before → After, Then Apply

ALWAYS show the diff before applying. Never silently overwrite.

Current description:
──────────────────────────────────────────────
<current body, or "(empty)" if blank>
──────────────────────────────────────────────

Proposed description:
──────────────────────────────────────────────
<new body>
──────────────────────────────────────────────

Use AskUserQuestion with a Yes/No question before applying:

Question: "Apply this description to PR #<NUMBER>?"
Options:  Yes | No

Only proceed if the user selects Yes. If No, ask what to change and re-draft.

Apply using the GitHub API directly:

gh api --method PATCH repos/{owner}/{repo}/pulls/<NUMBER> \
  --field body='## Motivation
...

## Technical Details
...

## Test Plan
- [ ] ...'

Resolve {owner}/{repo} with:

gh repo view --json nameWithOwner -q .nameWithOwner

To also update the title, add --field title='...' to the same call.

Verify the update:

gh pr view <NUMBER>

Red Flags — Stop and Correct

• About to call gh pr create — that recreates the PR. Use gh api --method PATCH.
• Using main as the base branch without reading baseRefName from the PR.
• Overwriting the body without reading and displaying the current content first.
• Applying changes without showing before/after and using AskUserQuestion Yes/No.

Common Mistakes