Allow the specification to use subdomain-based urls

There are two types of amazon urls:
http://mybucket.s3.amazonaws.com/keypath
http://s3.amazonaws.com/bucket/keypath

There are configurations such that if you ask for a file on the latter path, it will give you a 301 and tell you to access based on the subdomain-based path. It'd be great to specify how you want the url so you can avoid the extra hop.