Compiling files from several distinct directories into a single output

For reasons beyond my control, I have my source code in separate, unrelated directories. Like this:

diretorioPai
    foo
        serverSideJS
        clientSideJS
    bar
        serverSideJS
        clientSideJS

I've set up browserify (with watchify ) to use multiple entries and have only one output. My problem is that watchify only comes with a directory - the first in the list of entries. It does not detect changes in the second directory (nor others that I add). I already noticed that no error is triggered.

These are the relevant parts of my gulpfile :

gulp.task('js', function () {
    var dir1 = '/diretorioPai/foo/clientSideJS';
    var dir2 = '/diretorioPai/bar/clientSideJS'

    var opts = {
        entries: [dir1, dir2]
    }
    opts = xtend(opts, watchify.args);

    var bundler = browserify(opts);
    bundler = watchify(bundler);

    bundler.on('update', function (file) {
        gutil.log('Arquivo ' + file + ' alterado.');
        rebundle();
    });

    function rebundle () {
        return bundler
            .bundle()
            .on('error', function (e) {
                gutil.log('Error durante a compilação. : ' + e);
            })
            .on('finish', function (e) {
                gutil.log('Pronto.');
            })
            .pipe(source('app.js'))
            .pipe(gulp.dest('/diretorioDeSaida/JS'));
    }
    return rebundle();
});

How do I make browser , or at least browserify , track files in miscellaneous directories, and compile what I find in a single file?