s3cmd is slow, aws-cli can't handle prefixes, we can do better.
Building requires glide and go 1.6+ to be installed.
$ make dependencies
$ make build# Sync all objects to from my-bucket starting with my-prefix to dest-folder
$ s3sync s3://my-bucket/my-prefix dest-folder
# Server-side copy bucket A to bucket B
$ s3sync s3://A/my-prefix s3://B