fix: use *string for detailPrefix

Signed-off-by: Ruihua Wen <[email protected]>

Author: SpiffyEight77

pkg/cmd/container/logs.go

@@ -105,7 +105,7 @@ func Logs(ctx context.Context, client *containerd.Client, container string, opti
 				}
 			}
 
-			detailPrefix := ""
+			var detailPrefix string
 			if options.Details {
 				if logConfigJSON, ok := l["nerdctl/log-config"]; ok {
 					type logConfig struct {
@@ -154,7 +154,7 @@ func Logs(ctx context.Context, client *containerd.Client, container string, opti
 				Since:             options.Since,
 				Until:             options.Until,
 				Details:           options.Details,
-				DetailPrefix:      detailPrefix,
+				DetailPrefix:      &detailPrefix,
 			}
 			logViewer, err := logging.InitContainerLogViewer(l, logViewOpts, stopChannel, options.GOptions.Experimental)
 			if err != nil {

pkg/logging/log_viewer.go

@@ -87,7 +87,7 @@ type LogViewOptions struct {
 	Details bool
 
 	// DetailPrefix is the prefix added when Details is enabled.
-	DetailPrefix string
+	DetailPrefix *string
 }
 
 func (lvo *LogViewOptions) Validate() error {
@@ -157,13 +157,12 @@ func InitContainerLogViewer(containerLabels map[string]string, lvopts LogViewOpt
 // Prints all logs for this LogViewer's containers to the provided io.Writers.
 func (lv *ContainerLogViewer) PrintLogsTo(stdout, stderr io.Writer) error {
 	if lv.logViewingOptions.Details {
-		prefix := " "
-		if lv.logViewingOptions.DetailPrefix != "" {
-			prefix = lv.logViewingOptions.DetailPrefix + " "
+		if lv.logViewingOptions.DetailPrefix != nil {
+			prefix := *lv.logViewingOptions.DetailPrefix + " "
+			stdout = NewDetailWriter(stdout, prefix)
+			stderr = NewDetailWriter(stderr, prefix)
 		}
 
-		stdout = NewDetailWriter(stdout, prefix)
-		stderr = NewDetailWriter(stderr, prefix)
 	}
 	viewerFunc, err := getLogViewer(lv.loggingConfig.Driver)
 	if err != nil {