pr-writer - Claude MCP Skill

# PR Writer

Write the PR body as a cover note for reviewers, not a changelog, template,
validation log, or file-by-file summary.

## Inspect the Change

Requires authenticated `gh`. Inspect the current branch, working tree, PR,
base branch, commits, and full diff:

```bash
git branch --show-current
git status --porcelain
gh pr view --json number,title,body,url,baseRefName,headRefName
gh repo view --json defaultBranchRef
```

If `gh pr view` reports that no PR exists, continue with first-time PR
creation. For an existing PR, use its `baseRefName`; otherwise use the
repository default branch. Set `BASE`, then inspect:

```bash
git log "$BASE"..HEAD --oneline
git diff "$BASE"...HEAD
```

If on `main` or `master`, create a feature branch first. Ensure intended
changes are committed and review the whole branch diff, not only the latest
commit or existing PR text.

## Core Rules

- Describe concrete changed behavior, affected surfaces, and reviewer impact
  before implementation detail.
- Explain motivation, risk, tradeoffs, migration, or review focus only when
  useful.
- Use the smallest structure that makes the change easier to review.
- Replace internal prompt or process terminology with specific behavior.
- When refreshing a PR, rewrite around the current full diff without narrating
  review history.

## Titles

Use `<type>(<scope>): <subject>` or `<type>: <subject>`.

Allowed types: `feat`, `fix`, `ref`, `perf`, `docs`, `test`, `build`,
`ci`, `chore`, `style`, `meta`, `license`, and `revert`.

- Describe the dominant full-branch change with the narrowest accurate type
  and scope.
- Use `!` only when the change breaks an external contract, and explain the
  affected surface in the body.
- Avoid vague subjects such as `update`, `cleanup`, `misc`, `fix stuff`,
  or `address feedback`. Do not add a trailing period.
- Keep an existing title only when it still describes the whole diff.

## Body Shape

Choose the minimum useful shape:

| Change | Include |
|--------|---------|
| Small or obvious | One concise paragraph without headings. |
| Feature, bug fix, or refactor | Changed behavior and effect; add root cause, unchanged behavior, or non-obvious approach when relevant. |
| Contract or breaking change | Affected API, schema, payload, config, permission, storage, or CLI surface; include compatibility and migration guidance. |
| Operational, visual, or workflow change | User/operator effect, measured impact, failure modes, or flow when useful. |
| Broad, generated, or cross-cutting change | Organizing principle, why the breadth is necessary, and where review should start. |

Default:

```markdown
<What changed and what effect it has.>

<Why the approach, risk, migration, or review focus matters, if not obvious.>
```

For review-feedback updates, describe the resulting PR as a whole rather than
the sequence of revisions.

## Reviewer Aids

Use an aid only when it reduces reviewer reconstruction work:

- A compact before/after or interface example for changed contracts.
- A small Mermaid diagram for async flows or state transitions.
- A screenshot or recording note when visual evidence exists.
- A rollout, compatibility, risk, or review-order note when reviewers or
  adopters need it.

Introduce an artifact with one sentence explaining what reviewers should
notice. Omit it when prose is clearer.

## Boundaries

- Do not add default `Summary`, `Changes`, or `Test Plan` sections.
- Omit routine validation unless it changes risk assessment or explains
  meaningful regression coverage. For docs, skills, copy, or config changes,
  omit it by default.
- Do not paste commands, CI logs, validation dumps, commit logs, placeholders,
  or exhaustive file lists.
- Never include customer or organization names, user emails, support ticket
  contents, secrets, or PII.
- Use issue references only when verified from user input, branch names,
  commits, PR discussion, or tracker output. `Fixes <issue>` closes;
  `Refs <issue>` only links.

## Create or Update

Create new PRs as drafts. Write the body to a temporary Markdown file, then run:

```bash
gh pr create --draft --title '<title>' --body-file /tmp/pr-body.md
```

Update existing PRs with `gh api`:

```bash
gh api -X PATCH repos/{owner}/{repo}/pulls/PR_NUMBER \
  -f title='<title>' \
  -F body=@/tmp/pr-body.md
```

Refresh the title and body when follow-up commits materially change scope,
approach, breaking behavior, risk, migration, or review expectations. Skip
typo-only, formatting-only, and rename-only follow-ups.

## Examples

Small change:

```markdown
The AI Customizations section now starts collapsed so it does not consume
sidebar space before users need it. Expanding it preserves the existing saved
preference behavior.
```

Breaking contract:

````markdown
Run logs now emit chunk-level records instead of one skill-level record.
Consumers that read top-level `findings` must iterate over
`chunk.findings` for each record.

Before:

```json
{"skill": "security-review", "findings": [...]}
```

After:

```json
{"schemaVersion": 1, "chunk": {"index": 1, "findings": [...]}}
```
````