Implement template v2 feature of pushing to stack

common/framework/Template.php

@@ -30,6 +30,7 @@ class Template
 	public $vars;
 	protected $_fragments = [];
 	protected static $_loopvars = [];
+	protected static $_stacks = [];
 
 	/**
 	 * Static properties
@@ -411,6 +412,24 @@ class Template
 		}
 	}
 
+	/**
+	 * Get the contents of a stack.
+	 *
+	 * @param string $name
+	 * @return ?array
+	 */
+	public function getStack(string $name): ?array
+	{
+		if (isset(self::$_stacks[$name]))
+		{
+			return self::$_stacks[$name];
+		}
+		else
+		{
+			return null;
+		}
+	}
+
 	/**
 	 * Check if a path should be treated as relative to the path of the current template.
 	 *