Commit Message Generating

Generate and validate conventional commit messages for projects with high commit message quality requirements.

Requirements

• Git repository with commit history
• Explicit commit reference (any valid git ref)
• Optional: .commitmsgrc.md for custom project rules

Mode Detection

• Generation: "generate", "create", "write" or /commit-gen
• Validation: "validate", "check", "verify" or /commit-check

Configuration

Load .commitmsgrc.md from project root if present. Extract: types, scopes, require_scope, required_ticket_format, max_subject_length, require_body_for_breaking, add_attribution_footer.

Defaults: Types (feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert), Subject max 72 chars, Body required for breaking changes, Attribution footer disabled.

---

Generation Workflow

Step 1: Load Config and Resolve Reference

1. Read .commitmsgrc.md if present, use defaults otherwise
2. Resolve commit reference: git rev-parse --verify <ref>^{commit}
3. Get diff and file list: git show <sha> --format="" --name-status and git show <sha> --format=""

Error: Invalid ref → show git log --oneline -5

Step 2: Determine Type

Analyze diff to determine type. See Type Detection for decision tree and confidence rules.

• HIGH/MEDIUM confidence → use type directly
• LOW confidence → use AskUserQuestion with options from analysis
• Store breaking change indicators for later use

Step 3: Infer Scope

Infer scope from file paths. See Scope Detection for inference rules.

• HIGH/MEDIUM confidence → use scope directly
• LOW confidence → use AskUserQuestion
• Omit scope when redundant (docs type + README, style type, ci type, root configs)

Step 4: Craft Subject and Message

Subject rules: Imperative mood, lowercase, no period, max length from config, specific description.

Message format:

type(scope): subject

body (if complex changes or breaking)

BREAKING CHANGE: description (if breaking)
Refs: TICKET-123 (if required_ticket_format)

🤖 Generated with [Claude Code](https://claude.com/claude-code) (if add_attribution_footer)

Co-authored-by: Claude <model-name> <noreply@anthropic.com> (if add_attribution_footer)

Note: Use your actual model name (e.g., "Opus 4.5", "Sonnet 4") for <model-name>.

Step 5: Validate and Present

Quick self-check: type matches changes, scope matches files, subject is accurate. If issues found, fix and note. Present the generated message.

Output format: Brief analysis (type reasoning, scope reasoning, breaking changes), then the commit message.

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Validation Workflow

Step 1: Load Config and Get Commit

1. Read .commitmsgrc.md if present
2. Resolve commit reference and get: message, diff, files
3. Parse message: type, scope, breaking marker, subject, body, footer

Step 2: Format Compliance

Check against Conventional Commits spec and project config:

• Type in allowed list
• Scope format (kebab-case) and in allowed list if configured
• Subject: no period, lowercase after colon, imperative mood
• Breaking marker (!) has BREAKING CHANGE footer
• Subject length within limits

Step 3: Consistency Check

Analyze actual changes and compare:

• Type accuracy: Does type match change nature?
• Scope accuracy: Do files match claimed scope?
• Subject accuracy: Does subject describe changes?
• Breaking changes: Properly marked?

Step 4: Validate Body Quality

Validate body quality. See Body Validation for checks.

• Check presence requirements (required for breaking changes, recommended for 5+ files)
• Check content quality (WHY not WHAT)
• Check structure (blank line, line length)
• For breaking changes: verify migration instructions

Step 5: Generate Report

Format validation results directly using these templates:

Status Icons: PASS=✓, WARN=⚠, FAIL=✗

Concise (for batch operations):

Commit {hash}: {STATUS} {icon} ({N} issues)

Standard (default):

Commit Message Validation Report
=================================

Commit: {hash}
Message: "{message}"

Format Compliance: {STATUS} {icon}
Consistency Check: {STATUS} {icon}
  {Only WARN/FAIL items with icon prefix}
Body Quality: {STATUS} {icon}
  {Only WARN/FAIL items with icon prefix}

Recommendations:
  1. {First recommendation from failed checks}

Verbose (for complex issues):

• Include all check details with reasoning
• Add suggested improved message if issues found

Present the formatted report to user.

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Git Commands

Use these git commands directly:

# Resolve reference to SHA
git rev-parse --verify <ref>^{commit}

# Commit files and diff
git show <sha> --name-status --format=''
git show <sha> --format=''

# Commit message
git log -1 --format='%B' <sha>

---

Error Handling

• Not a git repo → suggest git init
• Invalid commit ref → show recent commits with git log --oneline -5
• Invalid config → warn, use defaults, continue

Output Guidelines

• Generation: Brief analysis, then commit message (no validation checkmarks)
• Validation: Formatted report with status, issues, recommendations
• Adapt verbosity: verbose for complex/uncertain, concise for batch operations