style: Avoid deep nesting for parsing the liquid tag in the block body

.rubocop_todo.yml

@@ -21,10 +21,6 @@ Lint/InheritException:
 Layout/LineLength:
   Max: 294
 
-# Offense count: 1
-Metrics/BlockNesting:
-  Max: 4
-
 # Offense count: 44
 Naming/ConstantName:
   Exclude:

lib/liquid/block_body.rb

@@ -60,6 +60,14 @@ module Liquid
       Usage.increment("liquid_tag_contains_outer_tag") unless $ERROR_INFO.is_a?(SyntaxError)
     end
 
+    private def parse_liquid_tag(markup, parse_context, &block)
+      liquid_tag_tokenizer = Tokenizer.new(markup, line_number: parse_context.line_number, for_liquid_tag: true)
+      parse_for_liquid_tag(liquid_tag_tokenizer, parse_context) do |end_tag_name, end_tag_markup|
+        next unless end_tag_name
+        self.class.unknown_tag_in_liquid_tag(end_tag_name, end_tag_markup, &block)
+      end
+    end
+
     private def parse_for_document(tokenizer, parse_context, &block)
       while (token = tokenizer.shift)
         next if token.empty?
@@ -79,11 +87,7 @@ module Liquid
           end
 
           if tag_name == 'liquid'
-            liquid_tag_tokenizer = Tokenizer.new(markup, line_number: parse_context.line_number, for_liquid_tag: true)
+            parse_liquid_tag(markup, parse_context, &block)
-            parse_for_liquid_tag(liquid_tag_tokenizer, parse_context) do |end_tag_name, end_tag_markup|
-              next unless end_tag_name
-              self.class.unknown_tag_in_liquid_tag(end_tag_name, end_tag_markup, &block)
-            end
             next
           end