Use a single custom annotation for export

Remove annotation prefix and add multiple index records
for manifests with multiple image names. This makes the
custom annotation more consistent with the OCI image
annotation. Additionally, ensure the OCI image annotation
always represents the tag (partial image name) as recommended
by the specification. The containerd image name annotation
will always contain the full image name.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

import.go

@@ -20,7 +20,6 @@ import (
 	"context"
 	"encoding/json"
 	"io"
-	"strings"
 
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/errdefs"
@@ -131,8 +130,8 @@ func (c *Client) Import(ctx context.Context, reader io.Reader, opts ...ImportOpt
 		}
 
 		for _, m := range idx.Manifests {
-			names := imageNames(m.Annotations, iopts.imageRefT)
-			for _, name := range names {
+			name := imageName(m.Annotations, iopts.imageRefT)
+			if name != "" {
 				imgs = append(imgs, images.Image{
 					Name:   name,
 					Target: m,
@@ -176,34 +175,16 @@ func (c *Client) Import(ctx context.Context, reader io.Reader, opts ...ImportOpt
 	return imgs, nil
 }
 
-func imageNames(annotations map[string]string, ociCleanup func(string) string) []string {
-	var names []string
-	for k, v := range annotations {
-		if k == ocispec.AnnotationRefName {
-			if ociCleanup != nil {
-				v = ociCleanup(v)
-			}
-			if v != "" {
-				names = appendSorted(names, v)
-			}
-		} else if k == images.AnnotationImageName || strings.HasPrefix(k, images.AnnotationImageNamePrefix) {
-			names = appendSorted(names, v)
-
+func imageName(annotations map[string]string, ociCleanup func(string) string) string {
+	name := annotations[images.AnnotationImageName]
+	if name != "" {
+		return name
+	}
+	name = annotations[ocispec.AnnotationRefName]
+	if name != "" {
+		if ociCleanup != nil {
+			name = ociCleanup(name)
 		}
 	}
-	return names
-}
-
-func appendSorted(arr []string, s string) []string {
-	for i, c := range arr {
-		if s < c {
-			arr = append(arr, "")
-			copy(arr[i+1:], arr[i:])
-			arr[i] = s
-			return arr
-		} else if s == c {
-			return arr
-		}
-	}
-	return append(arr, s)
+	return name
 }