Add spec for Artifacts

Signed-off-by: Aviral Takkar <aviral26@users.noreply.github.com>

Author: aviral26

go.mod

@@ -0,0 +1,5 @@
+module github.com/notaryproject/artifacts
+
+go 1.16
+
+require github.com/opencontainers/go-digest v1.0.0

go.sum

@@ -0,0 +1,2 @@
+github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8Oi/yOhh5U=
+github.com/opencontainers/go-digest v1.0.0/go.mod h1:0JzlMkj0TRzQZfJkVvzbP0HBR3IKzErnv2BNG4W4MAM=

specs-go/v2/artifact.go

@@ -0,0 +1,27 @@
+package v2
+
+import "github.com/notaryproject/artifacts/specs-go"
+
+// Artifact describes a registry artifact.
+// This structure provides `application/vnd.oci.artifact.manifest.v1+json` mediatype when marshalled to JSON.
+type Artifact struct {
+	specs.Versioned
+
+	// MediaType is the media type of the object this schema refers to.
+	MediaType string `json:"mediaType"`
+
+	// ArtifactType is the artifact type of the object this schema refers to.
+	ArtifactType string `json:"artifactType"`
+
+	// Config references the configuration of the object this schema refers to. It is optional.
+	Config *Descriptor `json:"config,omitempty"`
+
+	// Blobs is a collection of blobs referenced by this manifest.
+	Blobs []Descriptor `json:"blobs"`
+
+	// Manifests is a collection of manifests this artifact is linked to.
+	Manifests []Descriptor `json:"manifests"`
+
+	// Annotations contains arbitrary metadata for the artifact manifest.
+	Annotations map[string]string `json:"annotations,omitempty"`
+}

specs-go/v2/artifacttype.go

@@ -0,0 +1,6 @@
+package v2
+
+const (
+	// ArtifactTypeNotaryV2 specifies the artifact type for a notary V2 object.
+	ArtifactTypeNotaryV2 = "application/vnd.cncf.notary.v2"
+)

specs-go/v2/index.go

@@ -1,20 +1,6 @@
-// Copyright 2016 The Linux Foundation
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
 package v2
 
 const (
-	// MediaTypeImageIndex specifies the media type for an image index.
-	MediaTypeImageIndex = "application/vnd.oci.image.index.v2+json"
+	// MediaTypeArtifactManifest specifies the media type for an OCI artifact.
+	MediaTypeArtifactManifest = "application/vnd.oci.artifact.manifest.v1+json"
 )

specs-go/v2/mediatype.go

@@ -0,0 +1,9 @@
+package specs
+
+// Versioned provides a struct with the manifest schemaVersion and mediaType.
+// Incoming content with unknown schema version can be decoded against this
+// struct to check the version.
+type Versioned struct {
+	// SchemaVersion is the image manifest schema that this image follows
+	SchemaVersion int `json:"schemaVersion"`
+}