This allows users of a valid Digest to know it has a minimum of 2
characters in the hash part for use when sharding.
This is a reasonable restriction as the hash part is a SHA256 hash which
is 64 characters long, which is the common hash used. There is no
anticipation of using a hash with less than 2 characters.
Also, add MustParseDigest.
Also, replace Digest.Type with Digest.Split for getting both the type
and hash parts together, which is most the common case when asking for
either.
This commit adds path helpers for working with Names in URL and file
paths. The new helpers are ParseNameFromPath, ParseNameFromFilePath,
Name.Path, and Name.FilePath.
This commit also adds Name.DisplayLongest, and Name.DisplayLong.
Also, be it updates a place where strings.StripPrefix is more consistent
with the surrounding code.
Also, replace Parts with specific methods
