gulp-rev creates a directory inside the destination directory

Question

First of all, I would like to say that Gulp (for me) is creating more problems instead of solving them.

I wrote a gulpfile that concat some CSS files and put them inside a directory. The code for this task is the following:

var config = {
    mainDir: 'app/assets'
};

config.stylesFiles = [
    'bower_resources/admin-lte/dist/css/AdminLTE.min.css',
    'bower_resources/admin-lte/dist/css/skins/_all-skins.min.css',
    'css/app.css'
];

....

gulp.task('styles', function() {
    return gulp
        .src(config.stylesFiles, { cwd: config.mainDir })
        .pipe(sourcemaps.init())
            .pipe(concat('theme.css'))
        .pipe(sourcemaps.write('../build/css'))
        .pipe(gulp.dest('public/css/'))
        .on('end', function() { gutil.log('Styles copied') });
});

It is very simple and works perfectly.

But, I would like to version this generated file. So I wrote a specific task to do it:

....

config.manifestFolder = process.cwd() + '/public/build';

gulp.task('versionCSS', function() {
    return gulp
        .src(['css/theme.css'], { cwd: 'public' })
        .pipe(rev())
        .pipe(gulp.dest('public/build/css'))
        .pipe(rev.manifest( 
            {
                base: config.manifestFolder, 
                cwd: config.manifestFolder, 
                merge: true 
            } 
         ))
        .pipe(gulp.dest(config.manifestFolder))
        .on('end', function() { gutil.log('CSS files versioned') });
});

The problem is: when Gulp is going to run this task, it creates a folder inside the destination folder.

After running Gulp, I get this structure:

- public
  - build
    - css (destination folder for the versioned file)
      - css (folder created by Gulp)
        - versioned file that should be in the parent folder
  - css
    - concatenated file without version

I really don't know what to do anymore. I've already set the cwd and base options for the dest and src functions, changed the destinations, synchronized the tasks, etc. Nothing solves this stupid behavior.