Add path attribute to WikiFile class

Fixes #39420

changelogs/unreleased/fix-add-path-attr-to-wiki-file.yml

+---
+title: Fix broken wiki pages that link to a wiki file
+merge_request: 15019
+author:
+type: fixed

lib/gitlab/git/wiki_file.rb

 module Gitlab
   module Git
     class WikiFile
-      attr_reader :mime_type, :raw_data, :name
+      attr_reader :mime_type, :raw_data, :name, :path
 
       # This class is meant to be serializable so that it can be constructed
       # by Gitaly and sent over the network to GitLab.
@@ -13,6 +13,7 @@ module Gitlab
         @mime_type = gollum_file.mime_type
         @raw_data = gollum_file.raw_data
         @name = gollum_file.name
+        @path = gollum_file.path
       end
     end
   end

spec/lib/banzai/filter/gollum_tags_filter_spec.rb

@@ -15,9 +15,13 @@ describe Banzai::Filter::GollumTagsFilter do
 
   context 'linking internal images' do
     it 'creates img tag if image exists' do
-      file = Gollum::File.new(project_wiki.wiki)
-      expect(file).to receive(:path).and_return('images/image.jpg')
-      expect(project_wiki).to receive(:find_file).with('images/image.jpg').and_return(file)
+      gollum_file_double = double('Gollum::File',
+                                  mime_type: 'image/jpeg',
+                                  name: 'images/image.jpg',
+                                  path: 'images/image.jpg',
+                                  raw_data: '')
+      wiki_file = Gitlab::Git::WikiFile.new(gollum_file_double)
+      expect(project_wiki).to receive(:find_file).with('images/image.jpg').and_return(wiki_file)
 
       tag = '[[images/image.jpg]]'
       doc = filter("See #{tag}", project_wiki: project_wiki)