Remove tarsum support for digest package

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>

docs/storage/blob_test.go

@@ -20,16 +20,11 @@ import (
 // TestSimpleBlobUpload covers the blob upload process, exercising common
 // error paths that might be seen during an upload.
 func TestSimpleBlobUpload(t *testing.T) {
-	randomDataReader, tarSumStr, err := testutil.CreateRandomTarFile()
+	randomDataReader, dgst, err := testutil.CreateRandomTarFile()
 	if err != nil {
 		t.Fatalf("error creating random reader: %v", err)
 	}
 
-	dgst := digest.Digest(tarSumStr)
-	if err != nil {
-		t.Fatalf("error allocating upload store: %v", err)
-	}
-
 	ctx := context.Background()
 	imageName := "foo/bar"
 	driver := inmemory.New()
@@ -225,13 +220,11 @@ func TestSimpleBlobRead(t *testing.T) {
 	}
 	bs := repository.Blobs(ctx)
 
-	randomLayerReader, tarSumStr, err := testutil.CreateRandomTarFile() // TODO(stevvooe): Consider using just a random string.
+	randomLayerReader, dgst, err := testutil.CreateRandomTarFile() // TODO(stevvooe): Consider using just a random string.
 	if err != nil {
 		t.Fatalf("error creating random data: %v", err)
 	}
 
-	dgst := digest.Digest(tarSumStr)
-
 	// Test for existence.
 	desc, err := bs.Stat(ctx, dgst)
 	if err != distribution.ErrBlobUnknown {
@@ -358,7 +351,7 @@ func simpleUpload(t *testing.T, bs distribution.BlobIngester, blob []byte, expec
 
 	if dgst != expectedDigest {
 		// sanity check on zero digest
-		t.Fatalf("digest not as expected: %v != %v", dgst, digest.DigestTarSumV1EmptyTar)
+		t.Fatalf("digest not as expected: %v != %v", dgst, expectedDigest)
 	}
 
 	desc, err := wr.Commit(ctx, distribution.Descriptor{Digest: dgst})

docs/storage/blobwriter.go

@@ -302,7 +302,7 @@ func (bw *blobWriter) moveBlob(ctx context.Context, desc distribution.Descriptor
 			// get a hash, then the underlying file is deleted, we risk moving
 			// a zero-length blob into a nonzero-length blob location. To
 			// prevent this horrid thing, we employ the hack of only allowing
-			// to this happen for the zero tarsum.
+			// to this happen for the digest of an empty tar.
 			if desc.Digest == digest.DigestSha256EmptyTar {
 				return bw.blobStore.driver.PutContent(ctx, blobPath, []byte{})
 			}

docs/storage/cache/redis/redis.go

@@ -249,7 +249,7 @@ func (rsrbds *repositoryScopedRedisBlobDescriptorService) setDescriptor(ctx cont
 	}
 
 	// Also set the values for the primary descriptor, if they differ by
-	// algorithm (ie sha256 vs tarsum).
+	// algorithm (ie sha256 vs sha512).
 	if desc.Digest != "" && dgst != desc.Digest && dgst.Algorithm() != desc.Digest.Algorithm() {
 		if err := rsrbds.setDescriptor(ctx, conn, desc.Digest, desc); err != nil {
 			return err

docs/storage/linkedblobstore.go

@@ -282,7 +282,7 @@ func (lbs *linkedBlobStatter) Stat(ctx context.Context, dgst digest.Digest) (dis
 	}
 
 	if target != dgst {
-		// Track when we are doing cross-digest domain lookups. ie, tarsum to sha256.
+		// Track when we are doing cross-digest domain lookups. ie, sha512 to sha256.
 		context.GetLogger(ctx).Warnf("looking up blob with canonical target: %v -> %v", dgst, target)
 	}
 

docs/storage/paths.go

@@ -396,9 +396,8 @@ type layerLinkPathSpec struct {
 func (layerLinkPathSpec) pathSpec() {}
 
 // blobAlgorithmReplacer does some very simple path sanitization for user
-// input. Mostly, this is to provide some hierarchy for tarsum digests. Paths
-// should be "safe" before getting this far due to strict digest requirements
-// but we can add further path conversion here, if needed.
+// input. Paths should be "safe" before getting this far due to strict digest
+// requirements but we can add further path conversion here, if needed.
 var blobAlgorithmReplacer = strings.NewReplacer(
 	"+", "/",
 	".", "/",
@@ -468,10 +467,6 @@ func (repositoriesRootPathSpec) pathSpec() {}
 //
 // 	<algorithm>/<hex digest>
 //
-// Most importantly, for tarsum, the layout looks like this:
-//
-// 	tarsum/<version>/<digest algorithm>/<full digest>
-//
 // If multilevel is true, the first two bytes of the digest will separate
 // groups of digest folder. It will be as follows:
 //
@@ -494,19 +489,5 @@ func digestPathComponents(dgst digest.Digest, multilevel bool) ([]string, error)
 
 	suffix = append(suffix, hex)
 
-	if tsi, err := digest.ParseTarSum(dgst.String()); err == nil {
-		// We have a tarsum!
-		version := tsi.Version
-		if version == "" {
-			version = "v0"
-		}
-
-		prefix = []string{
-			"tarsum",
-			version,
-			tsi.Algorithm,
-		}
-	}
-
 	return append(prefix, suffix...), nil
 }

docs/storage/paths_test.go

@@ -2,8 +2,6 @@ package storage
 
 import (
 	"testing"
-
-	"github.com/docker/distribution/digest"
 )
 
 func TestPathMapper(t *testing.T) {
@@ -84,25 +82,6 @@ func TestPathMapper(t *testing.T) {
 			},
 			expected: "/docker/registry/v2/repositories/foo/bar/_manifests/tags/thetag/index/sha256/abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789/link",
 		},
-		{
-			spec: layerLinkPathSpec{
-				name:   "foo/bar",
-				digest: "tarsum.v1+test:abcdef",
-			},
-			expected: "/docker/registry/v2/repositories/foo/bar/_layers/tarsum/v1/test/abcdef/link",
-		},
-		{
-			spec: blobDataPathSpec{
-				digest: digest.Digest("tarsum.dev+sha512:abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789"),
-			},
-			expected: "/docker/registry/v2/blobs/tarsum/dev/sha512/ab/abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789/data",
-		},
-		{
-			spec: blobDataPathSpec{
-				digest: digest.Digest("tarsum.v1+sha256:abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789"),
-			},
-			expected: "/docker/registry/v2/blobs/tarsum/v1/sha256/ab/abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789/data",
-		},
 
 		{
 			spec: uploadDataPathSpec{