A script to install git hooks. Run these as the `postinstall` script in package.json. The example here writes a pre-commit hook that runs `npm test`. By having this as a self-contained script and not as a Grunt or Gulp task, Gulp or Grunt can be strict devDependencies.

writeHooksAsync.js

/* This script operates asynchronously. It can be written synchronously, but
 * not a lot is saved once you try-catch everything. Uses the async module.
 *
 * MIT licence.
 */
var fs = require('fs');
var path = require('path');
var async = require('async');

// Write as many of these as you like.
function writePreCommit(callback) {
	var filename = path.join(__dirname, '.git', 'hooks', 'pre-commit');
	var content = 'npm test';

	fs.writeFile(filename, content, function (err) {
		if (err) {
			return callback(err);
		}

		fs.chmod(filename, '755', callback);
	});
}

// Stack the write functions up in the parallel.
function writeHooks(callback) {
	async.parallel([
		writePreCommit
	], callback);
}

// Check that the git hooks directory exists. If it does, write the hooks and
// exit.
fs.stat(path.join(__dirname, '.git', 'hooks'), function (err, stat) {
	if (err || !stat.isDirectory()) {
		console.log('No git directory found. Hooks will not be installed.');
		return process.exit(0);
	}

	writeHooks(function (err) {
		if (err) {
			console.error(err);
			return process.exit(1);
		}

		console.log('Git hooks installed');
		process.exit(0);
	});
});

writeHooksCo.js

/* This script operates asynchronously. It can be written synchronously, but
 * not a lot is saved once you try-catch everything. Uses the co module. On
 * node 0.11.2+ with the --harmony flag generators are available. This
 * version uses Co, which requires generators.
 *
 * MIT licence.
 */
var path = require('path');
var co = require('co');
var fs = require('co-fs');


// Write the pre-commit script.
function* writePreCommit() {
	'use strict';

	var filename = path.join(__dirname, '.git', 'hooks', 'pre-commit');
	var content = 'npm test';

	var write = yield fs.writeFile(filename, content);
	var chmod = yield fs.chmod(filename, '755');

	return [write, chmod];
}

// Write the hook scripts in parallel.
function* writeHooks() {
	'use strict';

	// Stack more hook writers in here to write them in parallel.
	return yield [
		co(writePreCommit)
	];
}

// Check that the hooks directory exists and write the hooks.
function* execute() {
	'use strict';

	var stat = yield fs.stat(path.join(__dirname, '.git', 'hooks'));

	if (!stat.isDirectory()) {
		console.log('No git directory found. Hooks will not be installed.');
		return process.exit(0);
	}

	var hooks = yield co(writeHooks);

	return [stat, hooks];
}

// Execuse the writehoos.
co(execute)(function (err) {
	'use strict';

	if (err) {
		console.error(err);
		return process.exit(1);
	}

	console.log('Git hooks installed');
	process.exit(0);
});