install.js

const fs = require('fs');
const path = require('path');

const detectGitDir = require('./git-dir');

// Hard to catch this output if there's no new-line after the script runs.
process.on('exit', () => console.log());

function env(name) {
	if (!process.env[name]) {
		throw new Error(`Required environment variable is empty or not defined - are you using an NPM-compatible package manager?: ${name}`);
	}

	return process.env[name];
}

const nodeBin = env('npm_node_execpath');
const packageManagerBin = env('npm_execpath');

const gitDir = detectGitDir();

if (!gitDir || !fs.existsSync(gitDir) || !fs.statSync(gitDir).isDirectory()) {
	console.error('△  @vercel/git-hooks: .git directory not found or is not a directory; ignoring Git hook installation:', gitDir || 'reached filesystem boundary (root or drive)');
	process.exit(0);
}

const hooksDir = path.join(gitDir, 'hooks');

const hook = `#!/usr/bin/env bash
# !! AUTO-GENERATED FILE !!
# Do not edit manually. This file was generated by @vercel/git-hooks, located at ${__dirname}.

# These values were generated at install-time.
# If they are incorrect, either re-install the package's dependencies (by
# wiping node_modules), or submitting an issue at https://github.com/vercel/git-hooks/issues
# for any incorrect detection functionality.

set -euo pipefail

if [ ! -z "\${ZEIT_GITHOOKS_RUNNING-}" ]; then
	echo "△  ERROR: Refusing to run a nested git hook for fear of an endless loop." >&2
	echo "          You may \`unset ZEIT_GITHOOKS_RUNNING\` prior to running a nested" >&2
	echo "          Git command." >&2
	echo >&2
	exit 1
fi

export ZEIT_GITHOOKS_RUNNING=1

arg0="$(basename \${0})"

if [[ "\${arg0}" == "_do_hook.cjs" ]]; then
	echo "You probably didn't mean to call this directly." >&2
	exit 2
fi

"${nodeBin}" "$(dirname "\${0}")/_detect_package_hooks.cjs" "\${arg0}" | while IFS='' read -r hook || [[ -n "\${hook}" ]]; do
	echo "△  run hook: \${arg0} -> \${hook}" >&2
	if [[ $# -gt 0 ]]; then
		"${nodeBin}" "${packageManagerBin}" run "\${hook}" -- "$@"
	else
		"${nodeBin}" "${packageManagerBin}" run "\${hook}"
	fi
	echo >&2
done
`;

const hookDetector = `
const fs = require('fs');
const path = require('path');

const hook = process.argv[2];
const scriptHook = \`git-\${hook}\`;

const packagePath = path.join(__dirname, '../../package.json');
if (fs.existsSync(packagePath) && fs.statSync(packagePath).isFile()) {
	const pkg = require(packagePath);
	const hooks = [];

	if (pkg && typeof pkg.scripts === 'object' && scriptHook in pkg.scripts) {
		hooks.push(scriptHook);
	} else if (pkg && typeof pkg.git === 'object' && hook in pkg.git) {
		if (typeof pkg.git[hook] === 'string') {
			hooks.push(pkg.git[hook]);
		} else if (Array.isArray(pkg.git[hook])) {
			hooks.push(...pkg.git[hook]);
		}
	}

	if (hooks.length > 0) {
		console.log(hooks.join('\\n'));
	}
}
`;

// Create hooks directory if necessary
if (!fs.existsSync(hooksDir)) {
	fs.mkdirSync(hooksDir);
} else if (!fs.statSync(hooksDir).isDirectory()) {
	throw new Error(`@vercel/git-hooks: .git/hooks directory exists but is not a directory - this is most likely an error on your part: ${hooksDir}`);
}

// Write the hook and detector script
function writeExecutable(path, ...args) {
	fs.writeFileSync(path, ...args);
	fs.chmodSync(path, 0o755);
}

console.error(`△  @vercel/git-hooks: installing base hook to ${hooksDir}`);
writeExecutable(path.join(hooksDir, '_do_hook.cjs'), hook, 'utf-8');
writeExecutable(path.join(hooksDir, '_detect_package_hooks.cjs'), hookDetector, 'utf-8');

// Populate each of the hooks
function installHook(name) {
	const hookPath = path.join(hooksDir, name);

	if (fs.existsSync(hookPath)) {
		console.error(`△  @vercel/git-hooks: hook '${name}' already exists; skipping: ${hookPath}`);
		return;
	}

	fs.symlinkSync('./_do_hook.cjs', hookPath);
}

[
	'applypatch-msg',
	'pre-applypatch',
	'post-applypatch',
	'pre-commit',
	'prepare-commit-msg',
	'commit-msg',
	'post-commit',
	'pre-rebase',
	'post-checkout',
	'post-merge',
	'pre-push',
	'pre-receive',
	'update',
	'post-receive',
	'post-update',
	'push-to-checkout',
	'pre-auto-gc',
	'post-rewrite',
	'rebase',
	'sendemail-validate'
].forEach(installHook);

console.error('△  @vercel/git-hooks: hooks installed successfully');