Changelog writer

Changelog Writer

Turns git commits into changelog entries humans want to read. Covers the gap between "git log --oneline" (too technical) and "nothing" (too common).

When to Use

• Before a release, version bump, or deployment
• When a CHANGELOG.md needs updating
• When you need release notes for a blog post, email, or app store update
• When commits describe implementation but not user impact

When NOT to Use

• For internal-only changes with no user-visible effect
• For very first releases (no "since last release" baseline)

---

<process>

Phase 1: Determine the Scope

Ask or infer:

1. Git range — "since last release" (git tags), a specific SHA, or a branch diff. Default: git log $(git describe --tags --abbrev=0)..HEAD if tags exist, else git log HEAD~20..HEAD.
2. Audiences — which sections to generate. Default: all three (Users, Developers, Operators). Skip any that aren't relevant.
3. Format — CHANGELOG.md (Keep a Changelog format), Markdown for a blog post, or plain text for an email.
4. Version — if known, use it. Otherwise leave as [NEXT VERSION].

Detect git range automatically

# Check if tags exist
git describe --tags --abbrev=0 2>/dev/null && \
  echo "Use: git log $(git describe --tags --abbrev=0)..HEAD --pretty=format:'%H %s' --no-merges" || \
  echo "No tags found — use: git log HEAD~20..HEAD --pretty=format:'%H %s' --no-merges"

Phase 2: Read the Git History

Run:

git log <range> --pretty=format:"%H %s" --no-merges

For each commit, also read the full diff summary:

git show --stat <SHA>

Group commits by type if using conventional commits (feat, fix, docs, chore, refactor, perf, test, build, ci). Otherwise, read the commit message and classify by likely intent.

Phase 3: Classify and Draft

For each commit, decide:

Affects users? → Include in "Users" section

• New features, UI changes, behavior changes, bug fixes visible to users
• Write in plain English: "You can now do X" / "Fixed: X no longer happens"
• NEVER include: commit SHA, file names, function names, internal terminology

Affects developers integrating or extending? → Include in "Developers" section

• API changes, new hooks/events, SDK changes, breaking changes, new endpoints
• Can include technical terms, but explain impact: "Breaking: X now returns Y instead of Z"

Affects deployment, configuration, or operations? → Include in "Operators" section

• New environment variables, config changes, migration steps, infra changes
• Be specific: "New required env var: FEATURE_X_ENABLED (default: false)"

Internal only? → SKIP (refactors, test changes, CI changes, code style)

Transformation examples

Raw commit	Translated entry
fix: resolve null pointer in UserService.processPayment	Fixed a bug that caused payment processing to fail for some users.
feat: add dark mode toggle to settings panel	You can now switch to dark mode in Settings.
perf: replace O(n²) sort in feed ranking	Feeds with many items now load significantly faster.
chore: upgrade postgres driver to 16.x	(Operators) Updated database driver — no action required unless pinning the old version.
feat: add /v2/webhooks endpoint with retry logic	(Developers) New: /v2/webhooks endpoint with automatic retry on failure. See API docs.
refactor: extract PaymentGateway interface	SKIP — internal only.

Phase 4: Write the Entries

Rules for writing:

• Users section: Plain English. No jargon. Lead with the user benefit, not the implementation. Max 2 sentences per entry. Use "You can now...", "Fixed...", "Improved..."
• Developers section: Technical but clear. Always state the migration path for breaking changes.
• Operators section: Imperative and specific. "Set X to Y before deploying." "Run migration Z."
• No filler: Don't write "Various improvements and bug fixes" — if you can't describe it specifically, skip it.
• Group related items: Multiple commits fixing the same area → one entry.

Phase 5: Format Output

Keep a Changelog format (default)

## [NEXT VERSION] - YYYY-MM-DD

### For Users

- **New:** [feature description]
- **Fixed:** [bug fix description]
- **Changed:** [behavior change and why]

### For Developers

- **Breaking:** [what changed, how to migrate]
- **New:** [new API/hook/event]

### For Operators

- **Action required:** [what to do before deploying]
- **New config:** [variable name and purpose]

Blog post / email format

Omit the markdown headers. Write short prose paragraphs instead of bullet lists. Friendly tone, no technical filler.

If the user wants to update CHANGELOG.md

1. Read the existing file.
2. Identify the position of the # Changelog header (or top of file).
3. Prepend the new section immediately after the header, before any existing entries.
4. Preserve all existing content verbatim.
5. Offer to write it back.

Phase 6: Review Pass

Before presenting, check:

• Are all user-visible changes covered?
• Is there any internal jargon in the Users section?
• Are breaking changes clearly labeled?
• Would a non-technical user understand the Users section?

If any check fails, revise before presenting.

</process>

<anti_patterns>

Anti-Patterns

Don't	Do instead
Include commit SHAs or branch names in the Users section	Write about what the user experiences, not what the developer did
Write "Various improvements and bug fixes"	Name the specific fix or improvement, or skip it
Put refactors and test changes in any audience section	Internal changes have no changelog entry
Use function names, file names, or class names in the Users section	Translate to user experience: "payment processing" not "UserService.processPayment"
Write passive vague entries ("Performance has been improved")	Name the scenario: "Large dashboards now load in under 2 seconds"
Produce a Developers section entry without migration guidance for breaking changes	Always include "Before: X. After: Y. To migrate: Z."
Produce an Operators section entry without the exact variable name or command	Be specific: REDIS_MAX_CONNECTIONS=50 not "configure Redis appropriately"
Cover 0 commits in a section when none qualify	Omit the section entirely if it has no entries

</anti_patterns>

<success_criteria>

The changelog is complete when:

• Every user-visible change has an entry in plain English
• No commit SHAs, file names, or function names appear in the Users section
• Breaking changes are labeled and include a migration path
• Operator actions are imperative and specific
• Internal-only commits (refactors, CI, tests) are excluded
• Related commits are grouped, not listed individually
• The user has been offered to write/update CHANGELOG.md if applicable

</success_criteria>