[zendframework/zendframework#4105] Create proxy method headLink()

- Creates a proxy "headLink" method which allows us usage as described
  in the manual. Proxies to `__invoke`.

src/Helper/HeadLink.php

@@ -56,6 +56,21 @@ public function __construct()
         $this->setSeparator(PHP_EOL);
     }
 
+    /**
+     * Proxy to __invoke()
+     *
+     * Allows calling $helper->headLink(), but, more importantly, chaining calls
+     * like ->appendStylesheet()->headLink().
+     *
+     * @param  array  $attributes
+     * @param  string $placement
+     * @return HeadLink
+     */
+    public function headLink(array $attributes = null, $placement = Placeholder\Container\AbstractContainer::APPEND)
+    {
+        return call_user_func_array(array($this, '__invoke'), func_get_args());
+    }
+
     /**
      * headLink() - View Helper Method
      *

test/Helper/HeadLinkTest.php

@@ -92,16 +92,16 @@ public function testOffsetSetThrowsExceptionWithoutArrayArgument()
         $this->helper->offsetSet(1, 'foo');
     }
 
-    public function testCreatingLinkStackViaHeadScriptCreatesAppropriateOutput()
+    public function testCreatingLinkStackViaHeadLinkCreatesAppropriateOutput()
     {
         $links = array(
             'link1' => array('rel' => 'stylesheet', 'type' => 'text/css', 'href' => 'foo'),
             'link2' => array('rel' => 'stylesheet', 'type' => 'text/css', 'href' => 'bar'),
             'link3' => array('rel' => 'stylesheet', 'type' => 'text/css', 'href' => 'baz'),
         );
-        $this->helper->__invoke($links['link1'])
-                     ->__invoke($links['link2'], 'PREPEND')
-                     ->__invoke($links['link3']);
+        $this->helper->headLink($links['link1'])
+                     ->headLink($links['link2'], 'PREPEND')
+                     ->headLink($links['link3']);
 
         $string = $this->helper->toString();
         $lines  = substr_count($string, PHP_EOL);