# Quickstart: Copy-Paste Detection Quality Gate

## What This Feature Does

Adds automated copy-paste detection to the project's quality gates. When a developer commits code, jscpd scans for duplicated code blocks and blocks the commit if duplication exceeds the configured threshold. Developers can also run the scan on-demand.

## Key Commands

```bash
# Run copy-paste detection standalone
pnpm jscpd

# Run full quality gate (includes jscpd)
pnpm check

# Commit triggers the check automatically via Lefthook
git commit -m "my changes"
```

## Configuration

The jscpd configuration lives in `.jscpd.json` at the repo root. Key settings:

- **threshold**: Max allowed duplication percentage (default: 5%)
- **minLines**: Minimum lines for a duplicate block (default: 5)
- **minTokens**: Minimum tokens for a duplicate block (default: 50)
- **pattern**: File globs to scan (TypeScript/TSX)
- **ignore**: Directories/files to skip (node_modules, dist, etc.)

## How It Integrates

```
git commit → Lefthook pre-commit → pnpm check → knip + biome + tsc + vitest + jscpd
```

The `pnpm check` script is the single merge gate. jscpd is added to this chain, so it automatically runs as part of pre-commit hooks and any CI that uses `pnpm check`.