Common Changelog

Write human-facing changelog entries in Common Changelog format.

When to use

Use this skill when asked to generate, update, or normalize CHANGELOG.md from commits, PRs, or release notes.

When not to use

• Do not use for commit message wording; route to git-commits.
• Do not use for branch/rebase/PR process guidance; route to git-trunk-based-workflow.

Goal

Help readers answer: what changed and how it affects them.

Output contract

Choose exactly one output mode:

1. Full-file mode:
   • Use when the user asks to create, replace, or normalize an entire CHANGELOG.md.
   • Output MUST be a complete markdown file that starts with # Changelog.
2. Release-fragment mode:
   • Use when the user asks for a single release entry (for example 1.4.0 or Unreleased).
   • Output MUST contain exactly one release heading and its non-empty groups, unless FMT-9 applies and the release should be skipped due to no user-facing changes.

If user intent is ambiguous, default to release-fragment mode.

When metadata is incomplete, keep producing output and append:

Warnings:
- <warning 1>
- <warning 2>

Only include Warnings: when at least one warning exists. Warnings are out-of-band metadata and MUST appear after the primary changelog artifact.

Normative language

• MUST: mandatory requirement; fail output if violated
• SHOULD: recommended default; may be overridden only by explicit user instruction
• MAY: optional behavior

Canonical rules table

Use this table as the single source of truth for output structure and bullet formatting.

Input model

<type>[optional scope]: <description>

[optional body]

[optional footer(s)]

Recognize trailers and reference keywords:

• Category:
• Ref:
• Re:
• Co-authored-by:
• BREAKING CHANGE:

Also recognize GitHub issue-linking keywords:

• close, closes, closed
• fix, fixes, fixed
• resolve, resolves, resolved

For Ref, Re, and the keywords above:

• matching is case-insensitive
• : is optional (for example Ref ABC-123 and Ref: ABC-123 are both valid)
• treat GitHub keywords as reference signals only when an issue target is present (for example Fixes #123)

Classification algorithm

Apply in this order:

1. Category: trailer override
2. Conventional Commit type mapping
3. Semantic fallback

1) Category override (highest priority)

If Category: maps to a group, use it:

• change, changed -> Changed
• add, added -> Added
• remove, removed -> Removed
• fix, fixed -> Fixed

Rules:

• case-insensitive matching
• if multiple Category: trailers exist, use the last recognized one
• ignore unknown values and continue

2) Conventional Commits mapping

• feat -> Added
• fix -> Fixed
• perf -> Changed only if user-facing; otherwise skip
• refactor -> Changed only if user-facing; otherwise skip
• revert -> Changed or Fixed based on actual user effect
• docs, style, test, chore, ci, build -> skip unless user-facing

Type compatibility notes

• This skill classifies commit history, so it accepts both the strict type set used by git-commits and broader Conventional Commit variants observed in existing repositories.
• Accepted history-only variants include: perf, style, test, ci, build.
• This does NOT change the output type policy of git-commits; it only affects changelog classification of existing commits.

3) Semantic fallback

If type is missing or unclear:

• Existing behavior changed -> Changed
• New capability -> Added
• Capability removed -> Removed
• Bug corrected -> Fixed

Conflict examples

• fix(api): ... + Category: add -> Added
• feat!: + Category: remove -> Removed + **Breaking:**
• docs: + Category: fixed -> Fixed

Classification decision tree

1. If there is a recognized Category: value, map it and stop.
2. Else, if Conventional Commit type is recognized, apply the type mapping.
3. Else, classify by semantic user impact (Changed/Added/Removed/Fixed).
4. If breaking signal exists (! or BREAKING CHANGE:), prefix with **Breaking:**.

Breaking change handling

• If header has ! or body/footer contains BREAKING CHANGE:, prefix with **Breaking:**
• Keep the entry in Changed/Added/Removed/Fixed by impact (no extra section)

User-facing quick test

Usually include:

• API contract or output changed
• CLI flags/defaults changed
• Config shape/defaults changed
• Runtime/performance behavior users notice
• Dependency bump that fixes production bug/security issue

Usually skip:

• Internal refactor without behavior change
• CI/test/style-only updates
• Dev tooling and internal docs only
• Dependency bump for dev/test-only tooling

References and authors

• Commit hash SHOULD be a markdown link when available:
  • [`d23ba8f`](https://github.com/OWNER/REPO/commit/d23ba8f)
• Group formatting for references, commit links, and authors MUST follow BUL-3 and BUL-4
• Build references from:
  • explicit PR/issue links
  • Ref and Re trailers
  • GitHub keywords (close*, fix*, resolve*) with issue targets
• Normalize before deduplication:
  • treat #123 and https://github.com/OWNER/REPO/issues/123 as the same issue reference
  • normalize case for keyword-style references (for example jira-123 -> JIRA-123)
• Reference order is deterministic:
  1. first: one high-signal repository reference (prefer PR, otherwise issue)
  2. then: remaining unique references in first-seen order
• Commit-link order is deterministic:
  1. deduplicate by commit hash
  2. keep first-seen order
• Use commit author as primary author
• Append Co-authored-by: names (extract name before <email>)
• Authors MUST be deduplicated in stable first-seen order
• For aggregated bullets, authors MUST be the deduplicated union of commit authors and Co-authored-by: names from all included commits, preserving stable first-seen order
• If commit author is a bot and merger is known, prefer the human merger name

Metadata fallback policy

• If author cannot be determined from metadata, use (Unknown author) and emit a warning.
• If no commit link can be determined, use (source unavailable) as the commit-links group and emit a warning.
• Missing metadata MUST NOT be a sole reason to drop user-facing bullets.

Fail policy

• If any structural MUST rule is violated and cannot be recovered with fallback policy, fail.
• Missing author/commit metadata alone MUST NOT trigger hard fail.
• If changelog scope is unclear, default to release-fragment mode instead of failing.

Authoring workflow

1. Collect input: commits, PRs, issues, release notes.
2. Parse commit headers, body, and trailers.
3. Classify each change using rules above.
4. Remove non-user-facing noise and no-op pairs (change + immediate revert).
5. Rewrite into concise user-facing bullets.
6. Group by Changed, Added, Removed, Fixed in that order.
7. Validate against Canonical rules table and references/CHANGELOG.md.

Anti-patterns

• Raw technical commit text with no user context
• Non-standard sections (Security, Docs, Chore, etc.)
• Internal-only noise in public changelog
• Missing **Breaking:** marker for incompatible changes

Quality checklist

• Validate all applicable FMT-* and BUL-* requirements from Canonical rules table.
• Verify output shape against references/CHANGELOG.md.
• Ensure warning messages exist for every metadata fallback.
• Any checklist failure MUST trigger Fail policy.

Prompt templates

• Generate a Common Changelog entry for version <VERSION> from these commits and PRs. Keep only user-facing changes, include references, and mark breaking changes.
• Normalize this existing changelog fragment to Common Changelog format without losing important user-impact details.
• Classify these Conventional Commits into Changed/Added/Removed/Fixed and explain any skipped items.

References

• references/CHANGELOG.md (local formatting template)
• https://common-changelog.org/
• https://github.com/vweevers/common-changelog
• https://www.conventionalcommits.org/
• https://git-scm.com/docs/git-interpret-trailers
• https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword