Introduce shallow gitignore parsing for better performance

bench.js

@@ -29,6 +29,26 @@ const runners = [{
 	run: patterns => {
 		globbyMaster.sync(patterns);
 	}
+}, {
+	name: 'globby async gitignore (working directory)',
+	run: (patterns, cb) => {
+		globby(patterns, {gitignore: true}).then(cb.bind(null, null), cb);
+	}
+}, {
+	name: 'globby async gitignore (upstream/master)',
+	run: (patterns, cb) => {
+		globbyMaster(patterns, {gitignore: true}).then(cb.bind(null, null), cb);
+	}
+}, {
+	name: 'globby sync gitignore (working directory)',
+	run: patterns => {
+		globby.sync(patterns, {gitignore: true});
+	}
+}, {
+	name: 'globby sync gitignore (upstream/master)',
+	run: patterns => {
+		globbyMaster.sync(patterns, {gitignore: true});
+	}
 }, {
 	name: 'glob-stream',
 	run: (patterns, cb) => {
@@ -53,15 +73,18 @@ const benchs = [{
 	patterns: ['a/*', '!a/**']
 }, {
 	name: 'multiple positive globs',
-	patterns: ['a/*', 'b/*']
+	patterns: ['a/*', 'b/*', 'c/*']
 }];
 
 before(() => {
 	process.chdir(__dirname);
 	rimraf.sync(BENCH_DIR);
 	fs.mkdirSync(BENCH_DIR);
 	process.chdir(BENCH_DIR);
-	['a', 'b']
+
+	fs.writeFileSync('.gitignore', 'c');
+
+	['a', 'b', 'c']
 		.map(dir => `${dir}/`)
 		.forEach(dir => {
 			fs.mkdirSync(dir);

gitignore.js

@@ -1,12 +1,11 @@
 'use strict';
 const fs = require('fs');
 const path = require('path');
-const glob = require('glob');
 const gitIgnore = require('ignore');
+const multimatch = require('multimatch');
 const pify = require('pify');
 const slash = require('slash');
 
-const globP = pify(glob);
 const readFileP = pify(fs.readFile);
 
 const mapGitIgnorePatternTo = base => ignore => {
@@ -69,20 +68,38 @@ const normalizeOpts = opts => {
 	return {ignore, cwd};
 };
 
+const PASS_THROUGH = () => false;
+
 module.exports = o => {
 	const opts = normalizeOpts(o);
+	const rootIgnore = path.join(opts.cwd, '.gitignore');
+
+	if (opts.ignore.length > 0 && multimatch(rootIgnore, opts.ignore).length > 0) {
+		return Promise.resolve(PASS_THROUGH);
+	}
+
+	if (!fs.existsSync(rootIgnore)) {
+		return Promise.resolve(PASS_THROUGH);
+	}
 
-	return globP('**/.gitignore', {ignore: opts.ignore, cwd: opts.cwd})
-		.then(paths => Promise.all(paths.map(file => getFile(file, opts.cwd))))
-		.then(files => reduceIgnore(files))
+	return getFile('.gitignore', opts.cwd)
+		.then(file => reduceIgnore([file]))
 		.then(ignores => getIsIgnoredPredecate(ignores, opts.cwd));
 };
 
 module.exports.sync = o => {
 	const opts = normalizeOpts(o);
+	const rootIgnore = path.join(opts.cwd, '.gitignore');
+
+	if (opts.ignore.length > 0 && multimatch(rootIgnore, opts.ignore).length > 0) {
+		return PASS_THROUGH;
+	}
+
+	if (!fs.existsSync(rootIgnore)) {
+		return PASS_THROUGH;
+	}
 
-	const paths = glob.sync('**/.gitignore', {ignore: opts.ignore, cwd: opts.cwd});
-	const files = paths.map(file => getFileSync(file, opts.cwd));
-	const ignores = reduceIgnore(files);
+	const file = getFileSync('.gitignore', opts.cwd);
+	const ignores = reduceIgnore([file]);
 	return getIsIgnoredPredecate(ignores, opts.cwd);
 };

package.json

@@ -59,6 +59,7 @@
     "dir-glob": "^2.0.0",
     "glob": "^7.1.2",
     "ignore": "^3.3.5",
+    "multimatch": "^2.1.0",
     "pify": "^3.0.0",
     "slash": "^1.0.0"
   },