with a single ':', if possible. It is not an error, if the pattern
doesn't match (we return -1), but if there are two consecutive colons
'::', there must be a preceding ':[^:]+'. Hence, a volume path like
with a single ':', if possible. It is not an error, if the pattern
doesn't match (we return -1), but if there are two consecutive colons
'::', there must be a preceding ':[^:]+'. Hence, a volume path like