Print current plugin branch to admin bar

git-branch.php

<?php
public function admin_bar_menu() {

        global $wp_admin_bar;

        $plugin_path = ABSPATH . 'wp-content/plugins/WP-e-Commerce';

        exec( 'cd ' . $plugin_path . '  && git rev-parse --abbrev-ref HEAD', $output, $return );

        $wp_admin_bar->add_menu( array(
            'id' => 'wpec-branch',
            'title' => $output[0],
            'href' => false ) );
    }