Make passThroughOptions continue processing at unknown options

So that the help option is correctly consumed.

lib/command.js

@@ -1557,13 +1557,14 @@ Expecting one of '${allowedValues.join("', '")}'`);
         }
       }
 
-      // An unknown option means further arguments also classified as unknown so can be reprocessed by subcommands.
       if (maybeOption(arg)) {
+        // An unknown option means further arguments also classified as unknown so can be reprocessed by subcommands.
         dest = unknown;
-      }
-
-      // If using passThroughOptions, stop processing options at first command-argument / unknown option.
-      if (this._passThroughOptions) {
+      } else if (this._passThroughOptions) {
+        // If using passThroughOptions, stop processing options at first command-argument.
+        // Do not stop at unknown option
+        // - so that known options after it and before a subcommand / command-argument are consumed by the parent command (including the help option);
+        // - and because that is simply not what passThroughOptions is supposed to do.
         dest.push(arg, ...args);
         break;
       }