Gulp build for riot.js with sourcemaps

gulptfile.js

var es = require('event-stream'),
	gulp = require('gulp'),
	riot = require('gulp-riot'),
	rimraf = require('gulp-rimraf'),
	jshint = require('gulp-jshint'),
	stylus = require('gulp-stylus'),
	concat = require('gulp-concat'),
	uglify = require('gulp-uglify'),
	notify = require("gulp-notify"),
	plumber = require('gulp-plumber'),
	sourcemaps = require('gulp-sourcemaps');


var outName =	"app.js",
	build =		'./build',
	dest =		build + '/assets',
	tagSrc =	['./src/*.tag', './src/**/*.tag'],
	appSrc =	['./src/*.js', './src/**/*.js'],
	stylSrc =	['./src/*.styl'],
	copySrc =	['./src/*.html'],
	libSrc =	['./lib/**/*.js'],
	opts = 		{errorHandler: notify.onError("Error: <%= error.message %>")};


function libs() {return gulp.src(libSrc);}
function tags() {
	return gulp.src(tagSrc)
		.pipe(plumber())
		.pipe(riot());
}
function app() {return gulp.src(appSrc);}
function linted() {
	return es.merge(tags(), app())
		.pipe(plumber(opts))
		.pipe(jshint())
		.pipe(notify(function (file) {
			if (!file.jshint.success) {
				var errors = file.jshint.results.map(function (data) {
					if (data.error) {
						return "(" + data.error.line + ':' + data.error.character + ') ' + data.error.reason;
					}
				}).join("\n");
				return file.relative + " (" + file.jshint.results.length + " errors)\n" + errors;
			} else {
				return false;
			}
		}))
		.pipe(jshint.reporter('jshint-stylish'));
}

gulp.task('js', function() {
	return es.merge(libs(), linted())
		.pipe(plumber(opts))
		.pipe(sourcemaps.init())
		.pipe(concat(outName))
		.pipe(uglify())
		.pipe(sourcemaps.write('.'))
		.pipe(gulp.dest(dest));
});

gulp.task('copy', function () {
	return gulp.src(copySrc)
		.pipe(plumber(opts))
		.pipe(gulp.dest(build));
});

gulp.task('styl', function () {
	gulp.src(stylSrc)
		.pipe(plumber(opts))
		.pipe(sourcemaps.init())
		.pipe(stylus())
		.pipe(sourcemaps.write('.'))
		.pipe(gulp.dest(dest));
});

gulp.task('clean', function () {
	return gulp.src('build', {read: false})
		.pipe(plumber(opts))
		.pipe(rimraf({force: true}));
});

gulp.task('watch', function() {
	gulp.watch(copySrc.concat(appSrc, tagSrc, libSrc, stylSrc), ['copy', 'styl', 'js']);
});

gulp.task('default', ['copy', 'styl', 'js', 'watch']);