git-commit-message

Create a commit message for the staged changes. If changes are staged, return only the commit message, with no code fence or commentary. Otherwise, report that nothing is staged.

Inspect the staged changes

List the staged files:

<command> git diff --cached --name-only </command>

If this produces no output, report that nothing is staged and do not invent a message. Otherwise, read the complete staged diff:

<command> git diff --cached </command>

Use the conversation context to understand the rationale, but describe only the staged diff. Ignore unstaged and untracked changes.

Inspect the repository style

Read recent non-merge commit subjects before drafting the message:

<command> git log -30 --no-merges --format=%s </command>

Match the established style. Use Conventional Commit syntax such as feat(scope): ... or fix(scope): ... only when it clearly dominates recent history. Isolated examples and component prefixes such as subdir: ... do not establish that convention.

Use concise, natural language

• Prefer plain, slightly informal engineering language over formal wording.
• When unambiguous, prefer infra, config, prod, and dev over infrastructure, configuration, production, and development.
• Preserve exact names from the staged diff and follow established repository terminology when it differs.

Write the subject

• Limit the subject to 50 characters.
• Use the imperative mood: fix, not fixed or fixes.
• Do not end the subject with a period.
• When changes affect one clear component and history uses component prefixes, use <component>: <imperative summary> and match the casing used in recent history. Otherwise, capitalize the first word of an unprefixed subject.

Write the body

Use this format unless the subject fully describes one small, self-explanatory change:

<subject>

Changes:
- <change or rationale>
- <change or rationale>

• Separate the body from the subject with a blank line.
• Keep every body line within 72 characters, including indentation.
• Explain what changed and why without repeating the subject or including unnecessary implementation details.
• Use only as many bullets as needed; do not invent items to reach a fixed count.
• Do not end a one-line bullet with a period.
• Wrap bullets at word boundaries and indent continuation lines by two spaces.

Validate the message

Before returning the message, run scripts/validate_commit_message.py. Resolve its path relative to this SKILL.md directory and provide the draft through standard input or in a file:

python3 /path/to/git-commit-message/scripts/validate_commit_message.py \
  /path/to/draft-message

Revise and rerun the validator until it exits successfully. Never estimate line lengths manually.

Example

git-commit-message: improve guidance

Changes:
- Match subject formatting to established repository history
- Validate commit message formatting before returning the result
- Avoid Conventional Commit syntax unless the project clearly uses it