Conditional sourcemaps for browserify

gistfile1.js

var browserify = require('browserify');
var gulp = require('gulp');
var handleErrors = require('../util/handle-errors');
var source = require('vinyl-source-stream');

function createSingleBundle(options) {
    browserify({
        entries: options.input,
        extensions: options.extensions
    })
        .bundle({
            debug: process.env !== 'production'
        })
        .on('error', handleErrors)
        .pipe(source(options.output))
        .pipe(gulp.dest(options.destination));
}

function createBundles(bundles) {
    bundles.forEach(function(bundle) {
        createSingleBundle({
            input: bundle.input,
            output: bundle.output,
            extensions: bundle.extensions,
            destination: bundle.destination
        });
    });
}

gulp.task('browserify', function() {
    createBundles([{
        input: ['./client/javascript/app.js'],
        output: 'app.js',
        destination: './client/public/javascript/'
    }]);
});