feat(block): Support rendering parent block

CHANGELOG.md

@@ -49,6 +49,9 @@
   {% endfilter %}
   ```
 
+- You can now use `{{ block.super }}` to render a super block from another `{%
+  block %}`.
+
 ### Deprecations
 
 - `Template` initialisers have been deprecated in favour of using a template

Sources/Inheritence.swift

@@ -109,7 +109,9 @@ class BlockNode : NodeType {
 
   func render(_ context: Context) throws -> String {
     if let blockContext = context[BlockContext.contextKey] as? BlockContext, let node = blockContext.pop(name) {
-      return try node.render(context)
+      return try context.push(dictionary: ["block": ["super": self]]) {
+        return try node.render(context)
+      }
     }
 
     return try renderNodes(nodes, context)

Tests/StencilTests/InheritenceSpec.swift

@@ -18,5 +18,10 @@ func testInheritence() {
       let template = try environment.loadTemplate(name: "child-child.html")
       try expect(try template.render()) == "Child Child Header\nChild"
     }
+
+    $0.it("can inherit from a template that calls a super block") {
+      let template = try environment.loadTemplate(name: "child-super.html")
+      try expect(try template.render()) == "Header\nChild Body"
+    }
   }
 }

docs/templates.rst

@@ -128,6 +128,8 @@ A child template might look like the following:
       {% endfor %}
     {% endblock %}
 
+.. note:: You can use ``{{ block.super }}` inside a block to render the contents of the parent block inline.
+
 Since our child template doesn't declare a sidebar block. The original sidebar
 from our base template will be used. Depending on the content of ``notes`` our
 template might be rendered like the following: