commit-gen

A CLI tool that generates git commit messages from diffs using Claude.

How it works

1. Reads a git diff from stdin
2. Sends it to the Claude API with a prompt that enforces good commit message conventions
3. Streams the result back to stdout

Setup

npm install
cp .env.example .env
# Add your Anthropic API key to .env

Usage

# Generate message from staged changes
git diff --cached | node index.js

# Generate message from last commit
git diff HEAD | node index.js

# Stage everything and commit in one go
git add -A && git diff --cached | node index.js | git commit -F -

Tech

• Runtime: Node.js (ESM)
• AI: Claude via @anthropic-ai/sdk, streamed output
• Model: claude-sonnet-4-6

Output format

• First line: imperative mood, max 72 chars
• Optional body (blank line + 2–5 lines) explaining why, not what
• No vague words, no markdown, no preamble