Fix link with emoji

app/helpers/gitlab_markdown_helper.rb

@@ -21,7 +21,7 @@ module GitlabMarkdownHelper
 
     gfm_body = Gitlab::Markdown.gfm(escaped_body, project: @project, current_user: current_user)
 
-    fragment = Nokogiri::XML::DocumentFragment.parse(gfm_body)
+    fragment = Nokogiri::HTML::DocumentFragment.parse(gfm_body)
     if fragment.children.size == 1 && fragment.children[0].name == 'a'
       # Fragment has only one node, and it's a link generated by `gfm`.
       # Replace it with our requested link.

spec/helpers/gitlab_markdown_helper_spec.rb

@@ -106,6 +106,12 @@ describe GitlabMarkdownHelper do
       act = link_to_gfm(text, '/foo')
       expect(act).to eq %Q(<a href="/foo">#{issues[0].to_reference}</a>)
     end
+
+    it 'should replace commit message with emoji to link' do
+      actual = link_to_gfm(':book:Book', '/foo')
+      expect(actual).
+        to eq %Q(<img class="emoji" title=":book:" alt=":book:" src="http://localhost/assets/emoji/1F4D6.png" height="20" width="20" align="absmiddle"><a href="/foo">Book</a>)
+    end
   end
 
   describe '#render_wiki_content' do