etag, ok := metadata["etag"]
	if !ok {
		// md5Sum tag is kept for backward compatibility.
		etag = metadata["md5Sum"]
	}
	// Success.
	return etag
}

// HasPrefix - Prefix matcher string matches prefix in a platform specific way.
// For example on windows since its case insensitive we are supposed
// to do case insensitive checks.
func HasPrefix(s string, prefix string) bool {