docs: def cp(source, bucket, checksum, key_prefix):
      """Create new bucket from all files in directory."""
      from .models import Bucket
      from .helpers import populate_from_path
      for object_version in populate_from_path(
              Bucket.get(bucket), source, checksum=checksum,
              key_prefix=key_prefix):
          click.secho(str(object_version))
      db.session.commit()