tarsum is not actually used by the registry. Remove support for it.
Convert numerous uses in unit tests to SHA256.
Update docs to remove mentions of tarsums (which were often inaccurate).
Remove tarsum dependency.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
Previously a useful gist, this changeset polishes the original tarsum tool into
a utility that can be used to calculate content digests. Any algorithm from the
digest package is supported with additional support from tarsum.
This tool is very useful for quickly checking backend digests and verifying
correctness.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
