Allow providing manual signature hint to commands

src/Command.php

@@ -19,10 +19,13 @@ class Command
     /** @var callable $handler The handler */
     private $handler;
 
-    public function __construct(string $name, callable $handler)
+    private ?array $signature;
+
+    public function __construct(string $name, callable $handler, ?array $signature = null)
     {
         $this->name = $name;
         $this->handler = $handler;
+        $this->signature = $signature;
     }
 
     public function getName(): string
@@ -66,5 +69,10 @@ class Command
         return $args;
     }
 
+    public function getSignature(): array
+    {
+        return $this->signature ?? $this->parameters();
+    }
+
 }