imagetools: avoid pushing to same repo in parallel

If multiple tags are specified for the same repo, it is
wasteful to use them as separate targets and better to
make them share the blob upload phase of the push.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
(cherry picked from commit 917d7f2)

Author: tonistiigi

commands/imagetools/create.go

@@ -200,27 +200,39 @@ func runCreate(ctx context.Context, dockerCli command.Cli, in createOptions, arg
 	eg, _ := errgroup.WithContext(ctx)
 	pw := progress.WithPrefix(printer, "internal", true)
 
+	tagsByRepo := map[string][]reference.Named{}
 	for _, t := range tags {
+		repo := t.Name()
+		tagsByRepo[repo] = append(tagsByRepo[repo], t)
+	}
+
+	for repo, repoTags := range tagsByRepo {
 		eg.Go(func() error {
-			return progress.Wrap(fmt.Sprintf("pushing %s", t.String()), pw.Write, func(sub progress.SubLogger) error {
+			seed := repoTags[0]
+			return progress.Wrap(fmt.Sprintf("pushing %s", repo), pw.Write, func(sub progress.SubLogger) error {
 				baseCtx := ctx
 				eg2, _ := errgroup.WithContext(ctx)
 				for _, desc := range manifests {
 					eg2.Go(func() error {
 						ctx = withMediaTypeKeyPrefix(baseCtx)
-						sub.Log(1, fmt.Appendf(nil, "copying %s from %s to %s\n", desc.Digest.String(), desc.Source.Ref.String(), t.String()))
+						sub.Log(1, fmt.Appendf(nil, "copying %s from %s to %s\n", desc.Digest.String(), desc.Source.Ref.String(), repo))
 						return r.Copy(ctx, &imagetools.Source{
 							Ref:  desc.Source.Ref,
 							Desc: desc.Descriptor,
-						}, t)
+						}, seed)
 					})
 				}
 				if err := eg2.Wait(); err != nil {
 					return err
 				}
 				ctx = withMediaTypeKeyPrefix(ctx) // because of containerd bug this needs to be called separately for each ctx/goroutine pair to avoid concurrent map write
-				sub.Log(1, fmt.Appendf(nil, "pushing %s to %s\n", desc.Digest.String(), t.String()))
-				return r.Push(ctx, t, desc, dt)
+				for _, t := range repoTags {
+					sub.Log(1, fmt.Appendf(nil, "pushing %s to %s\n", desc.Digest.String(), t.String()))
+					if err := r.Push(ctx, t, desc, dt); err != nil {
+						return err
+					}
+				}
+				return nil
 			})
 		})
 	}