fastc

Zero-config CLI tool that analyses your git diff with an LLM and creates atomic, conventional commits.

$ fastc
✓ Staged 12 files
✓ Planned 3 commits
Planned commits:
──────────────────────────────────────────────────────────
1 feat(auth): add JWT token validation
src/auth.go, src/auth_test.go
2 refactor(db): extract connection pool config
src/db.go, src/config.go +2 more
3 chore: update lockfiles
go.sum
──────────────────────────────────────────────────────────
✓ feat(auth): add JWT token validation
✓ refactor(db): extract connection pool config
✓ chore: update lockfiles
✓ Pushed

Features

• Atomic commits - Groups related changes into logical commits
• Conventional commit format - feat, fix, refactor, chore, docs, style, test, perf
• Smart diff handling - Two-phase approach for large diffs (15+ files)
• Lockfile separation - Commits lockfiles separately with chore: update lockfiles
• Diff compression - Reduces token usage for large diffs while preserving context
• Retry with backoff - Automatic retry on API rate limits or transient errors
• Rename detection - Properly handles renamed files

Install

Requires uv.

# Clone and symlink (use absolute path)
git clone https://github.com/danwt/demo-fast-commit.git
cd demo-fast-commit && ln -s "$(pwd)/fc"~/.local/bin/fastc &&cd ..
# Create config
mkdir -p ~/.config/fast-commit
cat >~/.config/fast-commit/.env << 'EOF'OPENROUTER_API_KEY=sk-or-v1-your-key-hereMODEL=google/gemini-2.0-flash-001EOF

Get an API key from openrouter.ai/keys.

Usage

cd your-git-repo
fastc # analyse, commit, and push
fastc --dry-run # preview commits without executing
fastc --no-push # commit but don't push
fastc --no-verify # bypass pre-commit hooks
fastc --bulk # skip LLM, use smart file tree analysis
fastc --provider claude # route prompts through the Claude Code CLI

The tool will:

• Use staged changes if any exist
• Otherwise stage and commit all changes
• Push after committing (unless --no-push)

Config

~/.config/fast-commit/.env:

Variable	Description
OPENROUTER_API_KEY	Your OpenRouter API key (required for the default provider)
MODEL	Model to use (required for the default provider). Any model on OpenRouter works.
STRUCTURED_OUTPUT	Set to false to disable JSON mode (default: true)
CLAUDE_MODEL	Model for --provider claude (default: haiku)

Providers

fastc talks to OpenRouter over HTTP. fastc --provider claude shells out to the Claude Code CLI instead, which sends nothing to a third party and needs no API key, because it spends the Agent SDK credit attached to a Claude subscription.

Install the CLI from claude.com/code and log in with claude once. The prompt runs with --safe-mode, so repo CLAUDE.md files, skills, plugins, hooks and MCP servers are all ignored.

It is much slower: tens of seconds per request against 2 to 3 for a fast OpenRouter model. The model thinks before answering, that cannot be turned off through the CLI, and how long it thinks varies by up to 9x between identical runs. Each request is also a process holding about 450MB, so phase 2 runs 4 at a time rather than 32.

To keep the prompt small the claude path strips context lines from the diff, which cuts it by roughly a quarter, and uses a shorter form of the scope rules. Phase 2 asks for a subject only when a group holds a single file, and reuses that group's phase 1 hint as the commit body. Commit messages themselves are the same shape on both providers.

Recommended models

Model	Speed	Quality	Cost
google/gemini-2.0-flash-001	Fast	Good	Low
anthropic/claude-3.5-sonnet	Medium	Excellent	Medium
openai/gpt-4o-mini	Fast	Good	Low

How it works

1. Detect changes - Uses staged changes if any, otherwise stages everything
2. Exclude noise - Filters out lockfiles and generated files from analysis
3. Analyse diff - For small diffs, sends directly to LLM. For large diffs (15+ files), uses two-phase approach:
   • Phase 1: Send file summary to group files by logical change
   • Phase 2: Generate commit message for each group
4. Create commits - Stages files per group and commits with generated message
5. Commit lockfiles - Any lockfiles get a separate chore: update lockfiles commit
6. Push - Pushes all commits to remote

Excluded from analysis

These files are excluded from LLM analysis (but still committed):

• Lockfiles: pnpm-lock.yaml, package-lock.json, yarn.lock, bun.lockb, Cargo.lock, poetry.lock, Pipfile.lock, go.sum, composer.lock, Gemfile.lock
• Generated: *.min.js, *.min.css, *.map

Testing

uv run --with pytest pytest test_fc.py -v

Claude Code integration

Copy SKILL.md to your .claude/skills/fastc/ directory:

mkdir -p ~/.claude/skills/fastc
cp SKILL.md ~/.claude/skills/fastc/SKILL.md

Then invoke with /fastc in Claude Code.

License

MIT