Symfony2 automatic asset versioning. `nginx symfony version`

config_prod.yml

imports:
    - { resource: release.php }
    - { resource: config.yml }

framework:
    templating:
        assets_version: %release_version%
        assets_version_format: "assets/rev/%%2$s/%%1$s"

nginx.conf

location ~ assets/rev/ {
  rewrite ^(.*?)/assets/rev/(.*?)/(.*)$ $1/$3 break;
}

release.php

<?php
$root = $container->getParameter('kernel.root_dir');
$head = file_get_contents($root.'/../.git/HEAD');
preg_match('#^ref: (.+?)$#', $head, $matches);
$version = file_get_contents($root.'/../.git/'.$matches[1]);

$container->setParameter('release_version', substr($version, 0, 7));