• docker/referece: add IsFullIdentifier
• Changed oci layout transport to thread-safe destination
• add pkg/blobcache from Buildah
• blobcache: drop import on buildah/docker
• blobcache: drop history comment
• blobcache: make ClearCache() private
• blobcache: remove CacheLookupReferenceFunc
• blobcache: turn BlobCache into a struct
• blobcache: export clearCache
• Remove (unused and unreachable) keyring support
• Eliminate a goroutine
• Also introduces internal-only interfaces to allow extending the transport feature set in the future