git-commit-message

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SKILL.md (first lines)

# Git Commit Message Generator

**Auto-generates conventional commit messages from git diffs with tiered format enforcement**

## Purpose

Analyze staged git changes and generate concise, meaningful commit messages following a tiered Conventional Commits specification. This skill examines file modifications, additions, and deletions to infer the type and scope of changes, producing commit messages that match the importance of the change - from detailed documentation for critical features to concise messages for minor updates.

**Key Innovation**: Three-tier format system that balances thoroughness for critical commits (feat, fix, security) with efficiency for routine changes (docs, chore, style).

## When This Skill Activates

- When `/commit-msg` command is invoked
- When invoked from a `commit-msg`/`prepare-commit-msg` hook (if installed)
- When user requests commit message suggestions
- When analyzing changes before creating a commit

## Core Capabilities

**1. Diff Analysis**
- Parse `git diff --staged` output
- Identify modified, added, and deleted files
- Analyze code changes (additions, deletions, modifications)
- Detect patterns across multiple files

**2. Change Classification**
- Determine commit type from changes:
  - `feat`: New features or functionality
  - `fix`: Bug fixes
  - `security`: Security fixes or hardening
  - `refactor`: Code restructuring without behavior change
  - `docs`: Documentation changes
  - `style`: Formatting, whitespace, code style
  - `test`: Adding or modifying tests
  - `chore`: Build process, dependencies, tooling
  - `perf`: Performance improvements
  - `ci`: CI/CD configuration changes
  - `build`: Build system changes
  - `revert`: Reverting previous commits

**3. Scope Detection**
- Infer scope from file paths and patterns:
  - Directory names (e.g., `api`, `auth`, `ui`)
  - File name patterns (e.g., `*.test.js` → `tests`)
  - Framework conventions (e.g., `components/`, `services/`)

**4. Message Generation**
- Format: `type(scope): description`
- Enforce tier limits: Tier 1 summary max 50 chars; Tier 2/3 summary max 72 chars (ideal 50)
- Use imperative mood ("add" not "added")
- Focus on "what" and "why", not "how"
- Provide 2-3 alternative suggestions

## Tier System: Smart Format Enforcement

This skill uses a **three-tier format system** that matches message detail to commit criticality:

### Tier 1: Critical Commits (feat, fix, perf, security)

**Requirements**: Detailed documentation with impact statement

**Format**:
```
type(scope): summary line (max 50 chars)

- Detailed description point 1
- Detailed description point 2
- Detailed description point 3

This change [impact statement describing user-facing benefit or risk addressed].

Affected files/components:
- path/to/file1
- path/to/file2
```

**Why**: Features, fixes, and performance changes affect users directly and need thorough documentation for future reference and changelog generation.

### Tier 2: Standard Commits (refactor, test, build, ci)

**Requirements**: Brief context and file list

**Format**:
```
type(scope): summary line (max 72 chars)

Brief explanation of what changed and why (1-2 sentences).

Files: path/to/file1, path/to/file2
```

**Why**: Internal improvements need context for maintainability but don't require extensive documentation.

### Tier 3: Minor Commits (docs, style, chore)

**Requirements**: Summary line, optional description

**Format**:
```
type(scope): summary line (max 72 chars)

[Optional: Additional context if helpful]
```

**Why**: Documentation and routine maintenance are self-explanatory from the diff; verbose messages add noise.

## Workflow

```text
0. Pre-staging typecheck (if project uses TypeScript):
   - Run `tsc --noEmit` on changed files before staging
   - Fix type errors before committing (avoids pre-commit hook retry loops)
1. Get staged changes (staged only, not working tree):
   - git diff --staged --name-status
   - git diff --staged --stat
   - git diff --staged
2. Load config → frameworks/shared-skills/skills/git-commit-message/config.yaml
3. Analyze changes:
   - Count files modified/added/deleted

From artivilla/agents-config, MIT.

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