ConstReadonlyShort: "short"Short format: hex-encoded first 4 bytes of the digest (8 chars),
matching the reference Digest::short_description.
This is the default format.
ReadonlyFull: "full"Full format: complete 64 hex character digest.
ReadonlyUR: "ur"UR format: digest encoded as a UR string.
Specifies the format for displaying envelope digests in tree output.