redirect missing rails digested asset paths in nginx to a non digested version

redirect invalid asset paths

location ~* ^\/assets\/(?:.*\/)?([\w-]+)-[0-9a-f]+\.(ico|css|js|gif|jpe?g|png)$ {
 try_files $uri @missing_image;
}

location @missing_image {
  rewrite ^\/assets(.*)-[0-9a-f]+(\.\w+)$ /assets$1$2 permanent;
}