fix(cmd.help): usage label was printed even if no text

Author: adhocore

src/Helper/OutputHelper.php

@@ -196,11 +196,11 @@ protected function showHelp(string $for, array $items, string $header = '', stri
      *
      * It replaces $0 with actual command name and properly pads ` ## ` segments.
      *
-     * @param string|null $usage Usage description.
+     * @param string $usage Usage description.
      *
      * @return self
      */
-    public function showUsage(string $usage = null): self
+    public function showUsage(string $usage): self
     {
         $usage = \str_replace('$0', $_SERVER['argv'][0] ?? '[cmd]', $usage);
 

src/Input/Command.php

@@ -343,8 +343,11 @@ public function showHelp()
 
         $helper
             ->showArgumentsHelp($this->allArguments())
-            ->showOptionsHelp($this->allOptions(), '', 'Legend: <required> [optional] variadic...')
-            ->showUsage($this->_usage);
+            ->showOptionsHelp($this->allOptions(), '', 'Legend: <required> [optional] variadic...');
+
+        if ($this->_usage) {
+            $helper->showUsage($this->_usage);
+        }
 
         return $this->emit('_exit', 0);
     }