Release Notes Generator

Generate professional release notes following the Keep a Changelog standard.

Input: Previous tag (e.g., v0.0.1)

$ARGUMENTS

---

Analyze the changes thoroughly before generating release notes.

Gates

Do not invent tags, PR numbers, or links. Each row must pass before the work that depends on it.

When	Pass condition (evidence)	On fail
Before git log / git diff	git tag -l "$PREV_TAG" prints exactly one line matching PREV_TAG	Stop; report that the tag is missing—do not write changelog entries
Before categorizing	git rev-parse "$PREV_TAG^{commit}" exits 0	Stop; fix PREV_TAG or repo checkout
If using gh pr list	Command exits 0 and JSON is valid	Fall back to commit subjects + merge-commit URLs only; do not fabricate PR numbers
After Step 5 footer edits	Step 6 footer-gate exits 0 (both grep -q checks pass against the staged CHANGELOG.md)	Re-run footer edits from Step 5, then re-run Step 6 until it exits 0

Step 1: Gather Changes

Run these commands to collect information about changes since the provided tag:

# Store the previous tag
PREV_TAG="$ARGUMENTS"

# Gate: tag must exist (output must be non-empty and match PREV_TAG)
git tag -l "$PREV_TAG"
# If the line above prints nothing, STOP — do not continue below.

# Get the repo URL for PR links
git remote get-url origin

# List commits since last tag
git log ${PREV_TAG}..HEAD --pretty=format:"%h %s" --no-merges

# Get detailed diff stats
git diff ${PREV_TAG}..HEAD --stat

# List changed files by directory
git diff ${PREV_TAG}..HEAD --name-only | sort | uniq

Also gather PR information:

# Get merged PRs since the tag (requires gh CLI)
gh pr list --state merged --search "merged:>=$(git log -1 --format=%ci $PREV_TAG | cut -d' ' -f1)" --json number,title,author,labels

Step 2: Analyze and Categorize

Categorize each change into exactly one of these groups (in this order):

Category	Include	Exclude
Added	New features, new public APIs, new CLI commands	Internal utilities not exposed to users
Changed	Modified behavior, performance improvements, updated dependencies with user impact	Refactors with no behavior change
Deprecated	Features marked for future removal	-
Removed	Deleted features, removed public APIs	Removed internal code
Fixed	Bug fixes, error handling improvements	Test-only fixes
Security	Vulnerability patches, security hardening	-

Exclude entirely:

• CI/CD configuration changes (unless they affect users)
• Documentation-only changes (unless they reveal new features)
• Code style/formatting changes
• Test-only changes
• Internal refactors with no user-visible impact
• Merge commits

Step 3: Determine Version Number

Based on the changes, suggest the next version following Semantic Versioning:

• MAJOR (X.0.0): Breaking changes to public API
• MINOR (x.Y.0): New features, backward-compatible
• PATCH (x.y.Z): Bug fixes only

Detect the tag format from existing tags (with or without v prefix).

Step 4: Write Release Notes

Generate a CHANGELOG.md entry using this exact format:

## [VERSION] - YYYY-MM-DD

### Added

- **scope:** Add new feature description ([#54](REPO_URL/pull/54))

### Changed

- **Breaking:** Rename `oldName()` to `newName()` for consistency ([#145](REPO_URL/pull/145))

  **Migration:** Replace all calls to `oldName()` with `newName()`.

### Deprecated

- **scope:** Deprecate `legacy_function()` in favor of `new_function()` ([#143](REPO_URL/pull/143))

### Removed

- **Breaking:** Remove deprecated `old_function()` ([#141](REPO_URL/pull/141))

### Fixed

- **scope:** Fix race condition when multiple workers access shared state ([#139](REPO_URL/pull/139))

### Security

- **deps:** Update vulnerable package to patched version ([#49](REPO_URL/pull/49))

Writing Rules

Format requirements:

• Start every entry with an imperative verb: Add, Fix, Remove, Update, Improve, Rename, Deprecate, Patch
• Include scope prefix in bold when present: **server:**, **cli:**, **api:**
• One line per change (except breaking changes which get migration notes)
• Include PR/issue link at end of line
• Sort entries within each category by importance (most impactful first)
• Omit empty categories entirely

Breaking changes:

• Prefix with bold **Breaking:**
• List first within their category
• Add a **Migration:** block on the next line explaining exactly what users must change
• Include before/after code examples for API signature changes

Tone:

• Write for library consumers, not maintainers
• Focus on what changed for users, not how it was implemented
• Be specific—never write "various improvements" or "bug fixes"
• Each entry should be understandable without reading the PR

Bad examples to avoid:

# BAD - Too vague
- Fixed bugs
- Performance improvements
- Updated dependencies

# BAD - Implementation-focused
- Refactored the internal state machine to use async/await

# BAD - Missing context
- Fixed #234

Good examples to follow:

# GOOD - Specific and user-focused
- **server:** Fix timeout errors when processing files larger than 100MB ([#234](URL))
- **cli:** Add `--dry-run` flag to preview changes before execution ([#235](URL))
- **api:** Improve cold-start latency from 2.3s to 0.8s by lazy-loading plugins ([#236](URL))

Step 5: Update CHANGELOG.md

1. If CHANGELOG.md exists:

   • Insert new version after the ## [Unreleased] section (or at top if no Unreleased)

2. If CHANGELOG.md doesn't exist, create it with this header:

# Changelog

All notable changes to this project will be documented in this file.

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## [Unreleased]

3. Update the footer reference links at the bottom of the file. This step is mandatory — CodeRabbit and other reviewers will flag the changelog as incomplete if these are missing. Two edits are required:

   a. Advance [Unreleased] so it compares against the new version instead of the previous one. b. Insert a new [NEW_VERSION] line right below [Unreleased], comparing the previous tag to the new one.

   Example diff (releasing 3.2.0 after 3.1.0):

   -[Unreleased]: https://github.com/OWNER/REPO/compare/v3.1.0...HEAD
   +[Unreleased]: https://github.com/OWNER/REPO/compare/v3.2.0...HEAD
   +[3.2.0]: https://github.com/OWNER/REPO/compare/v3.1.0...v3.2.0
    [3.1.0]: https://github.com/OWNER/REPO/compare/v3.0.0...v3.1.0
   

   After editing, run Step 6 to verify both footer lines exist and are correct. Do not skip Step 6 — it is the hard gate that prevents the recurring "missing footer compare link" reviewer feedback.

Step 6: Verify CHANGELOG footer compare links (HARD GATE)

This is the enforcement gate for footer compare links. It must run before gen-release-notes reports success and before any commit step in the release workflow. It is not advisory — both grep -q checks must exit 0 or the gate fails with a named missing line.

Run this block exactly:

# Read the staged CHANGELOG.md blob (index), not the working tree, so unstaged
# edits cannot make the gate pass when the commit would actually fail.
STAGED_CHANGELOG=$(git show :CHANGELOG.md)

# Extract NEW and PREV versions from the staged CHANGELOG.md.
# We only match numeric `## [X.Y.Z]` headings so `## [Unreleased]` is skipped.
NEW_VERSION=$(printf '%s\n' "$STAGED_CHANGELOG" | grep -m1 -E '^## \[[0-9]+\.[0-9]+\.[0-9]+\]' | sed -E 's/^## \[([0-9]+\.[0-9]+\.[0-9]+)\].*/\1/')
PREV_VERSION=$(printf '%s\n' "$STAGED_CHANGELOG" | grep -m2 -E '^## \[[0-9]+\.[0-9]+\.[0-9]+\]' | sed -n '2p' | sed -E 's/^## \[([0-9]+\.[0-9]+\.[0-9]+)\].*/\1/')

if [ -z "$NEW_VERSION" ] || [ -z "$PREV_VERSION" ]; then
  echo "GATE FAIL: could not extract NEW_VERSION ($NEW_VERSION) or PREV_VERSION ($PREV_VERSION) from staged CHANGELOG.md"
  exit 1
fi

# Infer optional tag prefix (`v` or empty) from the existing [Unreleased] footer.
# Step 3 explicitly allows tags with or without `v`; never hardcode `v` here.
# Fall back to `v` only when no [Unreleased] footer exists yet (first release).
TAG_PREFIX=$(printf '%s\n' "$STAGED_CHANGELOG" | sed -nE 's|^\[Unreleased\]: .*/compare/(v?)[0-9]+\.[0-9]+\.[0-9]+\.\.\.HEAD$|\1|p' | head -1)
if ! printf '%s\n' "$STAGED_CHANGELOG" | grep -qE '^\[Unreleased\]:'; then
  TAG_PREFIX="v"
fi

echo "Gating footer compare links: NEW=${TAG_PREFIX}${NEW_VERSION}, PREV=${TAG_PREFIX}${PREV_VERSION}"

# Escape dots so they match literally inside the regex.
NEW_RE=${NEW_VERSION//./\\.}
PREV_RE=${PREV_VERSION//./\\.}

# Check 1: the new [NEW_VERSION] footer line exists and points PREV->NEW.
printf '%s\n' "$STAGED_CHANGELOG" | grep -qE "^\[${NEW_RE}\]: .*compare/${TAG_PREFIX}${PREV_RE}\.\.\.${TAG_PREFIX}${NEW_RE}\$" \
  || { echo "GATE FAIL: missing footer line: [${NEW_VERSION}]: .../compare/${TAG_PREFIX}${PREV_VERSION}...${TAG_PREFIX}${NEW_VERSION}"; exit 1; }

# Check 2: the [Unreleased] footer line is advanced to compare from the new tag.
printf '%s\n' "$STAGED_CHANGELOG" | grep -qE "^\[Unreleased\]: .*compare/${TAG_PREFIX}${NEW_RE}\.\.\.HEAD\$" \
  || { echo "GATE FAIL: [Unreleased] is not advanced; expected: [Unreleased]: .../compare/${TAG_PREFIX}${NEW_VERSION}...HEAD"; exit 1; }

echo "Footer compare links verified: [${NEW_VERSION}] and [Unreleased] both present and correct."

Pass condition (objective): both grep -q invocations above exit 0 against the staged CHANGELOG.md. The block must print Footer compare links verified: ... and exit 0.

On fail: the gate names the missing or wrong line. Return to Step 5 and edit CHANGELOG.md to add or correct that line, then re-run this block. Do not proceed to Step 7 or report success until the block exits 0.

Step 7: Output Summary

After updating the changelog, provide:

1. The suggested version number with rationale
2. Summary of categorized changes
3. Any breaking changes that need special attention
4. Confirmation that CHANGELOG.md was updated

Conventional Commits Mapping

Map commit prefixes to changelog categories:

Commit Prefix	Changelog Category
feat(scope):	Added
feat!(scope):	Added (with Breaking prefix)
fix(scope):	Fixed
perf(scope):	Changed
security(scope):	Security
docs:, chore:, ci:, test:, style:	Exclude