assoc

type Assoc interface {
	// Put associates the digest v with the key digest k of the provided
	// kind. If expect is nonzero, Put performs a compare-and-set,
	// erroring with errors.Precondition if the expected current value
	// was not equal to expect. Zero values indicate that the association
	// is to be deleted.
	Put(ctx context.Context, kind Kind, expect, k, v digest.Digest) error

	// Get returns the digest associated with key digest k and the
	// provided kind. Get returns an errors.NotExist when no such
	// mapping exists. Get expands the provided key when it is abbreviated,
	// and returns the expanded key when appropriate.
	Get(ctx context.Context, kind Kind, k digest.Digest) (kexp, v digest.Digest, err error)
}

type Kind int