added version number support

Makefile

@@ -1,4 +1,4 @@
-all: lint vet build
+all: lint vet build test
 
 build:
 	go build github.com/kopia/kopia/...

cas/format.go

@@ -2,6 +2,7 @@
 
 // Format describes the format of object data.
 type Format struct {
+	Version           string `json:"version"`
 	Hash              string `json:"hash"`
 	Encryption        string `json:"encryption"`
 	Secret            []byte `json:"secret,omitempty"`

cas/object_manager.go

@@ -127,6 +127,9 @@ func NewObjectManager(
 	f Format,
 	options ...ObjectManagerOption,
 ) (ObjectManager, error) {
+	if f.Version != "1" {
+		return nil, fmt.Errorf("unsupported repository version: %v", f.Version)
+	}
 	mgr := &objectManager{
 		repository:        r,
 		maxInlineBlobSize: f.MaxInlineBlobSize,

cas/object_manager_test.go

@@ -18,6 +18,7 @@
 
 func testFormat() Format {
 	return Format{
+		Version:           "1",
 		MaxBlobSize:       200,
 		MaxInlineBlobSize: 20,
 		Hash:              "md5",
@@ -355,59 +356,65 @@ func TestEndToEndReadAndSeek(t *testing.T) {
 func TestFormats(t *testing.T) {
 	cases := []struct {
 		format Format
-		hashes map[string]content.ObjectID
+		oids   map[string]content.ObjectID
 	}{
 		{
 			format: Format{
-				Hash: "md5",
+				Version: "1",
+				Hash:    "md5",
 			},
-			hashes: map[string]content.ObjectID{
+			oids: map[string]content.ObjectID{
 				"": "Cd41d8cd98f00b204e9800998ecf8427e",
 				"The quick brown fox jumps over the lazy dog": "C9e107d9d372bb6826bd81d3542a419d6",
 			},
 		},
 		{
 			format: Format{
-				Hash: "hmac-md5",
+				Version: "1",
+				Hash:    "hmac-md5",
 			},
-			hashes: map[string]content.ObjectID{
+			oids: map[string]content.ObjectID{
 				"": "C74e6f7298a9c2d168935f58c001bad88",
 				"The quick brown fox jumps over the lazy dog": "Cad262969c53bc16032f160081c4a07a0",
 			},
 		},
 		{
 			format: Format{
-				Hash:   "hmac-md5",
-				Secret: []byte("key"),
+				Version: "1",
+				Hash:    "hmac-md5",
+				Secret:  []byte("key"),
 			},
-			hashes: map[string]content.ObjectID{
+			oids: map[string]content.ObjectID{
 				"The quick brown fox jumps over the lazy dog": "C80070713463e7749b90c2dc24911e275",
 			},
 		},
 		{
 			format: Format{
-				Hash:   "hmac-sha1",
-				Secret: []byte("key"),
+				Version: "1",
+				Hash:    "hmac-sha1",
+				Secret:  []byte("key"),
 			},
-			hashes: map[string]content.ObjectID{
+			oids: map[string]content.ObjectID{
 				"The quick brown fox jumps over the lazy dog": "Cde7c9b85b8b78aa6bc8a7a36f70a90701c9db4d9",
 			},
 		},
 		{
 			format: Format{
-				Hash:   "hmac-sha256",
-				Secret: []byte("key"),
+				Version: "1",
+				Hash:    "hmac-sha256",
+				Secret:  []byte("key"),
 			},
-			hashes: map[string]content.ObjectID{
+			oids: map[string]content.ObjectID{
 				"The quick brown fox jumps over the lazy dog": "Cf7bc83f430538424b13298e6aa6fb143ef4d59a14946175997479dbc2d1a3cd8",
 			},
 		},
 		{
 			format: Format{
-				Hash:   "hmac-sha512",
-				Secret: []byte("key"),
+				Version: "1",
+				Hash:    "hmac-sha512",
+				Secret:  []byte("key"),
 			},
-			hashes: map[string]content.ObjectID{
+			oids: map[string]content.ObjectID{
 				"The quick brown fox jumps over the lazy dog": "Cb42af09057bac1e2d41708e48a902e09b5ff7f12ab428a4fe86653c73dd248fb82f948a549f7b791a5b41915ee4d1ec3935357e4e2317250d0372afa2ebeeb3a",
 			},
 		},
@@ -423,7 +430,7 @@ func TestFormats(t *testing.T) {
 			continue
 		}
 
-		for k, v := range c.hashes {
+		for k, v := range c.oids {
 			w := mgr.NewWriter()
 			w.Write([]byte(k))
 			oid, err := w.Result(true)