Revert "Merge pull request #325 from Shopify/remove-variable-incomplete-end"

That pull request broke raw tags with open variable tags. E.g.

{% raw %}
{{
{% endraw %}
{{ 1 }}

This reverts commit fbaabf3b59, reversing
changes made to af24d2c2ab.

lib/liquid.rb

@@ -24,17 +24,18 @@ module Liquid
   ArgumentSeparator           = ','
   FilterArgumentSeparator     = ':'
   VariableAttributeSeparator  = '.'
-  TagStart                    = '{%'
-  TagEnd                      = '%}'
+  TagStart                    = /\{\%/
+  TagEnd                      = /\%\}/
   VariableSignature           = /\(?[\w\-\.\[\]]\)?/
   VariableSegment             = /[\w\-]/
-  VariableStart               = '{{'
-  VariableEnd                 = '}}'
+  VariableStart               = /\{\{/
+  VariableEnd                 = /\}\}/
+  VariableIncompleteEnd       = /\}\}?/
   QuotedString                = /"[^"]*"|'[^']*'/
   QuotedFragment              = /#{QuotedString}|(?:[^\s,\|'"]|#{QuotedString})+/o
   TagAttributes               = /(\w+)\s*\:\s*(#{QuotedFragment})/o
   AnyStartingTag              = /\{\{|\{\%/
-  PartialTemplateParser       = /#{TagStart}.*?#{TagEnd}|#{VariableStart}.*?#{VariableEnd}/om
+  PartialTemplateParser       = /#{TagStart}.*?#{TagEnd}|#{VariableStart}.*?#{VariableIncompleteEnd}/om
   TemplateParser              = /(#{PartialTemplateParser}|#{AnyStartingTag})/om
   VariableParser              = /\[[^\]]+\]|#{VariableSegment}+\??/o
 end