8279785: JFR: 'jfr configure' should show default values

Reviewed-by: mgronlun

Author: egahlin

src/jdk.jfr/share/classes/jdk/jfr/internal/jfc/model/XmlFlag.java

@@ -29,7 +29,7 @@ final class XmlFlag extends XmlInput {
 
     @Override
     public String getOptionSyntax() {
-        return getName() + "=<true|false>";
+        return getName() + "=<true|false>" + "  (" + getContent() + ")";
     }
 
     @Override

src/jdk.jfr/share/classes/jdk/jfr/internal/jfc/model/XmlSelection.java

@@ -36,7 +36,15 @@ public String getOptionSyntax() {
         for (XmlOption option : getOptions()) {
             sj.add(option.getName());
         }
-        return getName() + "=" + sj.toString();
+        StringBuilder sb = new StringBuilder();
+        sb.append(getName());
+        sb.append("=");
+        sb.append(sj.toString());
+        XmlOption selected = getSelected();
+        if (selected != null) {
+            sb.append("  (").append(selected.getName()).append(")");
+        }
+        return sb.toString();
     }
 
     @Override

src/jdk.jfr/share/classes/jdk/jfr/internal/jfc/model/XmlText.java

@@ -34,6 +34,14 @@ public String getOptionSyntax() {
         sb.append("=<");
         sb.append(getContentType().orElse("text"));
         sb.append(">");
+        sb.append("  (");
+        String content = getContent();
+        if (isTimespan()) {
+            // "20 ms" becomes "20ms"
+            content = content.replaceAll("\\s", "");
+        }
+        sb.append(content);
+        sb.append(")");
         return sb.toString();
     }