c8d: Simplify error handling and distribution source label

Extract the distribution source label append into its own function and
make it not fail on any error, we do still log the error.

Signed-off-by: Djordje Lukic <djordje.lukic@docker.com>

daemon/containerd/image_push.go

@@ -157,36 +157,39 @@ func (i *ImageService) pushRef(ctx context.Context, targetRef reference.Named, m
 
 	err = remotes.PushContent(ctx, pusher, target, store, limiter, platforms.All, handlerWrapper)
 	if err != nil {
-		if containerdimages.IsIndexType(target.MediaType) {
-			if cerrdefs.IsNotFound(err) {
-				err = errdefs.NotFound(fmt.Errorf(
-					"missing content: %w\n"+
-						"Note: You're trying to push a manifest list/index which "+
-						"references multiple platform specific manifests, but not all of them are available locally "+
-						"or available to the remote repository.\n"+
-						"Make sure you have all the referenced content and try again.",
-					err))
-			}
-		}
-	} else {
-		appendSource, err := docker.AppendDistributionSourceLabel(realStore, targetRef.String())
-		if err != nil {
-			// This shouldn't happen at this point because the reference would have to be invalid
-			// and if it was, then it would error out earlier.
-			return errdefs.Unknown(errors.Wrap(err, "failed to create an handler that appends distribution source label to pushed content"))
+		if containerdimages.IsIndexType(target.MediaType) && cerrdefs.IsNotFound(err) {
+			return errdefs.NotFound(fmt.Errorf(
+				"missing content: %w\n"+
+					"Note: You're trying to push a manifest list/index which "+
+					"references multiple platform specific manifests, but not all of them are available locally "+
+					"or available to the remote repository.\n"+
+					"Make sure you have all the referenced content and try again.",
+				err))
 		}
+		return err
+	}
 
-		if err := containerdimages.Dispatch(ctx, appendSource, nil, target); err != nil {
-			// Shouldn't happen, but even if it would fail, then make it only a warning
-			// because it doesn't affect the pushed data.
-			log.G(ctx).WithError(err).Warn("failed to append distribution source labels to pushed content")
-		}
+	appendDistributionSourceLabel(ctx, realStore, targetRef, target)
+
+	i.LogImageEvent(reference.FamiliarString(targetRef), reference.FamiliarName(targetRef), events.ActionPush)
+
+	return nil
+}
+
+func appendDistributionSourceLabel(ctx context.Context, realStore content.Store, targetRef reference.Named, target ocispec.Descriptor) {
+	appendSource, err := docker.AppendDistributionSourceLabel(realStore, targetRef.String())
+	if err != nil {
+		// This shouldn't happen at this point because the reference would have to be invalid
+		// and if it was, then it would error out earlier.
+		log.G(ctx).WithError(err).Warn("failed to create an handler that appends distribution source label to pushed content")
+		return
 	}
 
-	if err == nil {
-		i.LogImageEvent(reference.FamiliarString(targetRef), reference.FamiliarName(targetRef), events.ActionPush)
+	if err := containerdimages.Dispatch(ctx, appendSource, nil, target); err != nil {
+		// Shouldn't happen, but even if it would fail, then make it only a warning
+		// because it doesn't affect the pushed data.
+		log.G(ctx).WithError(err).Warn("failed to append distribution source labels to pushed content")
 	}
-	return err
 }
 
 // findMissingMountable will walk the target descriptor recursively and return