// S3 ETag always consists of a 128 bit checksum
// value and an optional -<part-number> suffix.
// Therefore, s must have the following form in
// strict mode:  <32-hex-characters>[-<integer>]
//
// In non-strict mode, parse also accepts ETags
// that are not AWS S3 compatible - e.g. encrypted
// ETags.
func parse(s string, strict bool) (ETag, error) {
	// An S3 ETag may be a double-quoted string.