Agent Skills: Clean Commits

Clean Commits

Overview

Every commit is atomic, descriptive, and leaves code in a working state.

Core principle: Anyone should be able to checkout any commit and have working code.

Announce at use: "I'm committing with a descriptive message following clean-commits standards."

Commit Message Format

Structure

[type](scope): Short description (max 72 chars)

[Optional body - what and why, not how]

[Optional footer - issue references, breaking changes]

Refs: #[ISSUE_NUMBER]

Types

| Type | Use For | |------|---------| | feat | New feature | | fix | Bug fix | | docs | Documentation only | | style | Formatting, no code change | | refactor | Code restructuring | | test | Adding/fixing tests | | chore | Maintenance, dependencies |

Examples

feat(auth): Add user registration endpoint

Implement POST /api/users/register with email validation,
password hashing, and duplicate detection.

- Validates email format and uniqueness
- Hashes password with bcrypt
- Returns user object without password

Refs: #123

fix(auth): Prevent redirect loop on expired session

Session expiry was triggering redirect to login, which
checked session, found expired, and redirected again.

Now clears session cookie before redirecting.

Refs: #456

test(auth): Add integration tests for registration

Cover success case, duplicate email, invalid format,
and weak password scenarios.

Refs: #123

Atomic Commits

What Makes a Commit Atomic

| Atomic | Not Atomic | |--------|------------| | One logical change | Multiple unrelated changes | | Passes all tests | Breaks tests | | Complete feature slice | Half-implemented feature | | Can be reverted cleanly | Reverts would break things |

Signs of Non-Atomic Commits

• Commit message uses "and" to describe multiple things
• Diff includes unrelated files
• Some tests fail after commit
• "WIP" in commit message

Splitting Large Changes

If you have multiple changes, commit them separately:

# Stage specific files
git add src/auth/register.ts
git add src/auth/register.test.ts
git commit -m "feat(auth): Add registration endpoint"

# Stage next logical unit
git add src/auth/login.ts
git add src/auth/login.test.ts
git commit -m "feat(auth): Add login endpoint"

Working State Requirement

Every commit must leave the codebase in a state where:

• [ ] All tests pass
• [ ] Build succeeds
• [ ] Application runs
• [ ] No TypeScript errors
• [ ] No linting errors

Before committing:

# Run tests
pnpm test

# Check build
pnpm build

# Check types
pnpm typecheck

# Check lint
pnpm lint

If any fail, fix before committing.

Commit Frequency

Commit Often

• After each passing test in TDD cycle
• After each refactoring step
• After completing a logical unit

Don't Wait Too Long

| Too Infrequent | Just Right | |----------------|------------| | "Implement entire feature" | "Add user model" | | "Fix all bugs" | "Fix session expiry redirect" | | "Update everything" | "Update auth dependencies" |

Small is Good

Smaller commits are:

• Easier to review
• Easier to revert
• Easier to bisect
• Easier to understand

The Commit Process

1. Stage Selectively

# Review what changed
git diff

# Stage specific files
git add [specific files]

# Or stage interactively
git add -p

2. Review Staged Changes

# See what will be committed
git diff --staged

3. Write Descriptive Message

# Short message (if simple)
git commit -m "fix(auth): Handle null user in session check"

# Long message (if complex)
git commit
# Opens editor for full message

4. Verify After Commit

# Check commit looks right
git show --stat

# Verify tests still pass
pnpm test

Commit Message Body

When to include a body:

• Why the change was made (not just what)
• Context that isn't obvious from code
• Trade-offs or alternatives considered
• Breaking changes if any

Body Examples

refactor(api): Extract validation middleware

Validation logic was duplicated across 12 endpoints.
Extracted to reusable middleware that can be composed.

Alternative considered: validation library.
Rejected because our rules are domain-specific.

fix(data): Use optimistic locking for updates

Race condition was causing lost updates when two users
edited the same record simultaneously.

BREAKING CHANGE: Update operations now require
version field in request body.

Issue References

Always reference the issue:

# In commit message
Refs: #123

# Or if commit closes the issue
Closes: #123

Amending Commits

When to Amend

• Typo in message (if not pushed)
• Forgot to stage a file (if not pushed)

# Amend last commit (before push only!)
git add forgotten-file.ts
git commit --amend

When NOT to Amend

• After pushing to remote
• Changing commits others have based work on

Revert, Don't Delete

If a commit was wrong:

# Create a new commit that undoes the change
git revert [commit-sha]

# DON'T rewrite history on shared branches
# DON'T force push to fix mistakes

Checklist

Before each commit:

• [ ] Tests pass
• [ ] Build succeeds
• [ ] Change is atomic (one logical unit)
• [ ] Message follows format
• [ ] Message describes why, not just what
• [ ] Issue is referenced
• [ ] No "WIP" or placeholder messages

Integration

This skill is called by:

• issue-driven-development - Throughout development
• pr-creation - Before creating PR

This skill enforces:

• Reviewable history
• Revertible changes
• Clear project narrative