diff --git a/cli.js b/cli.js
index 57add500..4a83b7b3 100755
--- a/cli.js
+++ b/cli.js
@@ -79,7 +79,7 @@ updateNotifier({pkg: cli.pkg}).notify();
 const input = cli.input;
 const opts = cli.flags;
 
-function log(report) {
+const log = report => {
 	// legacy
 	// TODO: remove in 1.0.0
 	if (opts.compact) {
@@ -92,7 +92,7 @@ function log(report) {
 	process.exit(report.errorCount === 0 ? 0 : 1);
 }
 
-function open(report) {
+const open = report => {
 	if (report.errorCount === 0) {
 		return;
 	}
@@ -110,11 +110,7 @@ Fix it by setting path to your editor of choice in ~/.bashrc or ~/.zshrc:
 	}
 
 	const executableName = editor.split(path.sep).pop();
-
-	function lineColumn(message) {
-		return `${message.line}:${message.column}`;
-	}
-
+	const lineColumn = message => `${message.line}:${message.column}`;
 	const args = [];
 
 	report.results
diff --git a/index.js b/index.js
index 7be1cb32..df24c965 100644
--- a/index.js
+++ b/index.js
@@ -27,8 +27,8 @@ exports.lintText = (str, opts) => {
 	}
 
 	if (opts.filename) {
-		const gitIgnores = optionsManager.getGitIgnores(opts);
 		const filename = path.relative(opts.cwd, opts.filename);
+		const gitIgnores = optionsManager.getGitIgnores(opts);
 		const glob = [filename].concat(gitIgnores);
 
 		if (multimatch(glob, opts.ignores).length > 0) {
@@ -51,15 +51,11 @@ exports.lintText = (str, opts) => {
 	return processReport(report, opts);
 };
 
-exports.lintFiles = (pattern, opts) => {
+exports.lintFiles = (patterns, opts) => {
 	opts = optionsManager.preprocess(opts);
-
-	if (pattern.length === 0) {
-		pattern = '**/*';
-	}
+	patterns = patterns.length === 0 ? ['**/*'] : Array.isArray(patterns) ? patterns : [patterns];
 
 	const gitIgnores = optionsManager.getGitIgnores(opts);
-	const patterns = Array.isArray(pattern) ? pattern : [pattern];
 	const glob = patterns.concat(gitIgnores);
 
 	return globby(glob, {ignore: opts.ignores, nodir: true}).then(paths => {
diff --git a/options-manager.js b/options-manager.js
index aec09a3a..8ab8ad12 100644
--- a/options-manager.js
+++ b/options-manager.js
@@ -42,7 +42,7 @@ const DEFAULT_CONFIG = {
 	}
 };
 
-function normalizeOpts(opts) {
+const normalizeOpts = opts => {
 	opts = Object.assign({}, opts);
 
 	// Alias to help humans
@@ -75,25 +75,23 @@ function normalizeOpts(opts) {
 	return opts;
 }
 
-function mergeWithPkgConf(opts) {
+const mergeWithPkgConf = opts => {
 	opts = Object.assign({cwd: process.cwd()}, opts);
 	const conf = pkgConf.sync('xo', {cwd: opts.cwd, skipOnFalse: true});
 	return Object.assign({}, conf, opts);
 }
 
 // Define the shape of deep properties for deepAssign
-function emptyOptions() {
-	return {
-		rules: {},
-		settings: {},
-		globals: [],
-		envs: [],
-		plugins: [],
-		extends: []
-	};
-}
-
-function buildConfig(opts) {
+const emptyOptions = () => ({
+	rules: {},
+	settings: {},
+	globals: [],
+	envs: [],
+	plugins: [],
+	extends: []
+});
+
+const buildConfig = opts => {
 	const config = deepAssign(
 		emptyOptions(),
 		DEFAULT_CONFIG,
@@ -173,7 +171,7 @@ function buildConfig(opts) {
 // The hash value is a binary representation of which elements in the `overrides` array apply to the path.
 //
 // If overrides.length === 4, and only the first and third elements apply, then our hash is: 1010 (in binary)
-function findApplicableOverrides(path, overrides) {
+const findApplicableOverrides = (path, overrides) => {
 	let hash = 0;
 	const applicable = [];
 
@@ -192,12 +190,14 @@ function findApplicableOverrides(path, overrides) {
 	};
 }
 
-function mergeApplicableOverrides(baseOptions, applicableOverrides) {
-	return deepAssign.apply(null, [emptyOptions(), baseOptions].concat(applicableOverrides.map(normalizeOpts)));
+const mergeApplicableOverrides = (baseOptions, applicableOverrides) => {
+	applicableOverrides = applicableOverrides.map(normalizeOpts);
+	const overrides = [emptyOptions(), baseOptions].concat(applicableOverrides);
+	return deepAssign.apply(null, overrides);
 }
 
 // Creates grouped sets of merged options together with the paths they apply to.
-function groupConfigs(paths, baseOptions, overrides) {
+const groupConfigs = (paths, baseOptions, overrides) => {
 	const map = {};
 	const arr = [];
 
@@ -220,35 +220,32 @@ function groupConfigs(paths, baseOptions, overrides) {
 	return arr;
 }
 
-function getIgnores(opts) {
+const getIgnores = opts => {
 	opts.ignores = DEFAULT_IGNORE.concat(opts.ignores || []);
 	return opts;
 }
 
-function getGitIgnores(opts) {
-	const gitignores = globby.sync('**/.gitignore', {
+const getGitIgnores = opts => globby
+	.sync('**/.gitignore', {
 		ignore: opts.ignores || [],
 		cwd: opts.cwd || process.cwd()
-	});
-
-	return gitignores
-		.map(pathToGitignore => {
-			const patterns = parseGitignore(pathToGitignore);
-			const base = path.dirname(pathToGitignore);
-
-			return patterns
-				.map(pattern => {
-					const negate = !pattern.startsWith('!');
-					const patternPath = negate ? pattern : pattern.substr(1);
-					return {negate, pattern: path.join(base, patternPath)};
-				})
-				.sort(pattern => pattern.negate ? 1 : -1)
-				.map(item => item.negate ? `!${item.pattern}` : item.pattern);
-		})
-		.reduce((a, b) => a.concat(b), []);
-}
-
-function preprocess(opts) {
+	})
+	.map(pathToGitignore => {
+		const patterns = parseGitignore(pathToGitignore);
+		const base = path.dirname(pathToGitignore);
+
+		return patterns
+			.map(pattern => {
+				const negate = !pattern.startsWith('!');
+				const patternPath = negate ? pattern : pattern.substr(1);
+				return {negate, pattern: path.join(base, patternPath)};
+			})
+			.sort(pattern => pattern.negate ? 1 : -1)
+			.map(item => item.negate ? `!${item.pattern}` : item.pattern);
+	})
+	.reduce((a, b) => a.concat(b), []);
+
+const preprocess = opts => {
 	opts = mergeWithPkgConf(opts);
 	opts = normalizeOpts(opts);
 	opts = getIgnores(opts);