Initialize the references result Hash in ReferenceFilter

lib/gitlab/markdown/reference_filter.rb

@@ -12,7 +12,15 @@ module Gitlab
     #   :reference_class    - Custom CSS class added to reference links.
     #   :only_path          - Generate path-only links.
     #
+    # Results:
+    #   :references - A Hash of references that were found and replaced.
     class ReferenceFilter < HTML::Pipeline::Filter
+      def initialize(*args)
+        super
+
+        result[:references] = Hash.new { |hash, type| hash[type] = [] }
+      end
+
       def escape_once(html)
         ERB::Util.html_escape_once(html)
       end
@@ -29,6 +37,14 @@ module Gitlab
         context[:project]
       end
 
+      # Add a reference to the pipeline's result Hash
+      #
+      # type  - Singular Symbol reference type (e.g., :issue, :user, etc.)
+      # value - Object to add
+      def push_result(type, value)
+        result[:references][type].push(value)
+      end
+
       def reference_class(type)
         "gfm gfm-#{type} #{context[:reference_class]}".strip
       end