update vendoring dependencies

vendor/github.com/docker/distribution/digest/verifiers.go

@@ -3,9 +3,6 @@ package digest
 import (
 	"hash"
 	"io"
-	"io/ioutil"
-
-	"github.com/docker/docker/pkg/tarsum"
 )
 
 // Verifier presents a general verification interface to be used with message
@@ -27,70 +24,10 @@ func NewDigestVerifier(d Digest) (Verifier, error) {
 		return nil, err
 	}
 
-	alg := d.Algorithm()
-	switch alg {
-	case "sha256", "sha384", "sha512":
-		return hashVerifier{
-			hash:   alg.Hash(),
-			digest: d,
-		}, nil
-	default:
-		// Assume we have a tarsum.
-		version, err := tarsum.GetVersionFromTarsum(string(d))
-		if err != nil {
-			return nil, err
-		}
-
-		pr, pw := io.Pipe()
-
-		// TODO(stevvooe): We may actually want to ban the earlier versions of
-		// tarsum. That decision may not be the place of the verifier.
-
-		ts, err := tarsum.NewTarSum(pr, true, version)
-		if err != nil {
-			return nil, err
-		}
-
-		// TODO(sday): Ick! A goroutine per digest verification? We'll have to
-		// get the tarsum library to export an io.Writer variant.
-		go func() {
-			if _, err := io.Copy(ioutil.Discard, ts); err != nil {
-				pr.CloseWithError(err)
-			} else {
-				pr.Close()
-			}
-		}()
-
-		return &tarsumVerifier{
-			digest: d,
-			ts:     ts,
-			pr:     pr,
-			pw:     pw,
-		}, nil
-	}
-}
-
-// NewLengthVerifier returns a verifier that returns true when the number of
-// read bytes equals the expected parameter.
-func NewLengthVerifier(expected int64) Verifier {
-	return &lengthVerifier{
-		expected: expected,
-	}
-}
-
-type lengthVerifier struct {
-	expected int64 // expected bytes read
-	len      int64 // bytes read
-}
-
-func (lv *lengthVerifier) Write(p []byte) (n int, err error) {
-	n = len(p)
-	lv.len += int64(n)
-	return n, err
-}
-
-func (lv *lengthVerifier) Verified() bool {
-	return lv.expected == lv.len
+	return hashVerifier{
+		hash:   d.Algorithm().Hash(),
+		digest: d,
+	}, nil
 }
 
 type hashVerifier struct {
@@ -105,18 +42,3 @@ func (hv hashVerifier) Write(p []byte) (n int, err error) {
 func (hv hashVerifier) Verified() bool {
 	return hv.digest == NewDigest(hv.digest.Algorithm(), hv.hash)
 }
-
-type tarsumVerifier struct {
-	digest Digest
-	ts     tarsum.TarSum
-	pr     *io.PipeReader
-	pw     *io.PipeWriter
-}
-
-func (tv *tarsumVerifier) Write(p []byte) (n int, err error) {
-	return tv.pw.Write(p)
-}
-
-func (tv *tarsumVerifier) Verified() bool {
-	return tv.digest == Digest(tv.ts.Sum(nil))
-}