composer/composer — pull request #1647 by till (2013-03-03 14:44:49+00:00)
Title: Support downloads on Amazon S3 in private buckets

* calls abstracted in Composer\Util\AWS
* adds the AWS PHP SDK (2.x) as a dependency for the heavy lifting
* is used when the dist url starts with `s3://` or as a failover
* will/should not be used for regular dist urls (http://, https://) and public buckets