We found some examples of manifests with URLs specififed that did
not provide a digest or size. This breaks the security model by allowing
the content to change, as it no longer provides a Merkle tree. This
was not intended, so explicitly disallow by tightening wording.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
(cherry picked from commit 1660df4b60)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
19b573a6f7