Fix Markdown links not showing up in dashboard activity feed

Closes #2586

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 v 8.0.0 (unreleased)
+  - Fix Markdown links not showing up in dashboard activity feed (Stan Hu)
   - Fix HTML link that was improperly escaped in new user e-mail (Stan Hu)
   - Fix broken sort in merge request API (Stan Hu)
   - Bump rouge to 1.10.1 to remove warning noise and fix other syntax highlighting bugs (Stan Hu)

app/helpers/gitlab_markdown_helper.rb

@@ -45,7 +45,7 @@ module GitlabMarkdownHelper
   end
   def markdown(text, context = {})
-    context.merge!(
+    context.reverse_merge!(
       current_user: current_user,
       path:         @path,
       project:      @project,
@@ -59,7 +59,7 @@ module GitlabMarkdownHelper
   # TODO (rspeicher): Remove all usages of this helper and just call `markdown`
   # with a custom pipeline depending on the content being rendered
   def gfm(text, options = {})
-    options.merge!(
+    options.reverse_merge!(
       current_user: current_user,
       path:         @path,
       project:      @project,

spec/helpers/gitlab_markdown_helper_spec.rb

@@ -38,6 +38,17 @@ describe GitlabMarkdownHelper do
         expect(markdown(actual)).to match(expected)
       end
     end
+
+    describe "override default project" do
+      let(:actual) { issue.to_reference }
+      let(:second_project) { create(:project) }
+      let(:second_issue) { create(:issue, project: second_project) }
+
+      it 'should link to the issue' do
+        expected = namespace_project_issue_path(second_project.namespace, second_project, second_issue)
+        expect(markdown(actual, project: second_project)).to match(expected)
+      end
+    end
   end
   describe '#link_to_gfm' do