Clarify cached-image readiness errors and note SDK follow-up

Author: chruffins

pkg/cmd/pushcmd.go

@@ -115,8 +115,10 @@ func handleRemotePushTarget(ctx context.Context, cmd *cli.Command, target string
 	fmt.Fprintf(os.Stderr, "Docker image %s not available (%v); trying the Hypeman cache...\n", target, loadErr)
 	cachedImage, err := client.Images.Get(ctx, url.PathEscape(target))
 	if err == nil {
+		// A cached record that never became ready deserves a push-specific
+		// message; the shared helper's "image build failed" reads odd here.
 		if err := waitForImageReady(ctx, &client, cachedImage); err != nil {
-			return err
+			return fmt.Errorf("cached image %s is not ready: %w", target, err)
 		}
 		return runRemotePush(ctx, cmd, target, target)
 	}

pkg/cmd/tag.go

@@ -42,6 +42,8 @@ func handleTag(ctx context.Context, cmd *cli.Command) error {
 
 	var res []byte
 	opts = append(opts, option.WithResponseBodyInto(&res))
+	// TODO: switch to a typed Images.Tag once the tag API from kernel/hypeman#453
+	// is generated into hypeman-go.
 	body := struct {
 		Target string `json:"target"`
 	}{Target: target}