commit-message-storyteller skill

Commit Message Storyteller

Transforms raw git diffs and change descriptions into clear, story-driven commit messages that follow the Conventional Commits specification. Instead of "update file.js", you get messages that communicate intent, context, and impact.

When to Use This Skill

• User says "write a commit message"
• User pastes a git diff or describes code changes
• User says "what should I commit this as?" or "summarize my diff"
• User wants better commit history for their team or open-source project
• User is preparing a pull request and wants meaningful commit messages

Prerequisites

Have at least one of the following ready:

• Output from git diff or git diff --staged
• A description of what you changed and why
• A list of modified files

How It Works

Step 1: Gather the Change Context

Ask the user (or infer from the diff) for:

1. What changed — files, functions, logic affected
2. Why it changed — bug fix, new feature, refactor, performance, etc.
3. Who/what triggered it — issue number, user request, tech debt, etc.

If the user provides a raw git diff, extract this context automatically from the diff.

Step 2: Identify the Commit Type

Map the change to a Conventional Commits type using this guide:

Type	Use When
feat	A new feature or capability is added
fix	A bug or incorrect behavior is corrected
refactor	Code restructured without changing behavior
perf	A change that improves performance
docs	Documentation only changes
style	Formatting, whitespace, missing semicolons (no logic change)
test	Adding or updating tests
build	Build system or dependency changes
chore	Other maintenance that does not change source or tests
ci	CI/CD pipeline changes
revert	Reverting a previous commit

See references/conventional-commits-guide.md for detailed examples.

Step 3: Write the Commit Message

Follow this structure:

<type>(<optional scope>): <short imperative summary>

<body — the story: why this change was made, what problem it solves>

<footer — issue refs, breaking change notices>

Rules for Each Part

Subject line (first line):

• Use imperative mood: "add", "fix", "remove" — not "added" or "fixes"
• Max 72 characters
• No period at the end
• Lowercase after the colon

Body (the story):

• Explain the why, not the what (the diff already shows the what)
• Describe the problem that existed before this change
• Mention any alternatives considered if relevant
• Keep lines under 100 characters
• Separate from subject with a blank line

Footer:

• Reference issues: Closes #123, Fixes #456, Refs #789
• Mark breaking changes: BREAKING CHANGE: <description>

Step 4: Generate Output

Produce the commit message in a copyable code block, followed by a one-line plain-English explanation of the story you told.

Example output:

fix(auth): prevent token refresh loop on expired sessions

When a user's session expired mid-request, the auth middleware was
triggering a token refresh, which itself failed validation and triggered
another refresh — causing an infinite retry loop that crashed the app.

This adds a recursion guard flag that aborts the refresh cycle if a
refresh is already in progress, returning a clean 401 instead.

Closes #312

Story told: A silent infinite loop on session expiry was crashing the app; this stops the cycle early and returns a clean error.

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Multiple Commits from One Diff

If the diff contains logically separate changes, split them into multiple commit messages and tell the user. Use this heuristic:

• Different files with unrelated purposes → likely separate commits
• Same file but distinct concerns (e.g., bug fix + refactor) → suggest splitting
• Everything tightly coupled → one commit is fine

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Edge Cases

Situation	How to Handle
User provides no context beyond a diff	Infer type and scope from file names and changed symbols
Changes span many files with no clear theme	Ask: "Is this one logical change, or multiple?"
Breaking change detected	Add BREAKING CHANGE: footer automatically
User says "keep it short"	Omit body, just write a strong subject line
No issue number available	Omit the footer entirely

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Quick Reference

# Get your staged diff to paste into Copilot
git diff --staged

# Or get the last uncommitted working tree changes
git diff

See references/conventional-commits-guide.md for type examples and scope guidelines.