Fix broken templated "Too many changes to show" text

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23230
broke the external string in 11.6. This fixes that and
adds a spec.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/56138

app/views/projects/diffs/_warning.html.haml

@@ -9,4 +9,4 @@
         = link_to _("Plain diff"), merge_request_path(@merge_request, format: :diff), class: "btn btn-sm"
         = link_to _("Email patch"), merge_request_path(@merge_request, format: :patch), class: "btn btn-sm"
   %p
-    = _("To preserve performance only <strong>%{display_size} of ${real_size}</strong> files are displayed.").html_safe % { display_size: diff_files.size, real_size: diff_files.real_size }
+    = _("To preserve performance only <strong>%{display_size} of %{real_size}</strong> files are displayed.").html_safe % { display_size: diff_files.size, real_size: diff_files.real_size }

changelogs/unreleased/sh-fix-real-size-warnings.yml

+---
+title: Fix broken templated "Too many changes to show" text
+merge_request: 24282
+author:
+type: fixed

locale/gitlab.pot

@@ -7200,7 +7200,7 @@ msgstr ""
 msgid "To move or copy an entire GitLab project from another GitLab installation to this one, navigate to the original project's settings page, generate an export file, and upload it here."
 msgstr ""
-msgid "To preserve performance only <strong>%{display_size} of ${real_size}</strong> files are displayed."
+msgid "To preserve performance only <strong>%{display_size} of %{real_size}</strong> files are displayed."
 msgstr ""
 msgid "To start serving your jobs you can add Runners to your group"

spec/features/projects/compare_spec.rb

@@ -87,6 +87,21 @@ describe "Compare", :js do
       expect(find(".js-compare-from-dropdown .dropdown-content")).to have_selector("li", count: 3)
     end
+
+    context 'when commit has overflow', :js do
+      it 'displays warning' do
+        visit project_compare_index_path(project, from: "feature", to: "master")
+
+        allow(Commit).to receive(:max_diff_options).and_return(max_files: 3)
+        allow_any_instance_of(DiffHelper).to receive(:render_overflow_warning?).and_return(true)
+
+        click_button('Compare')
+
+        page.within('.alert') do
+          expect(page).to have_text("Too many changes to show. To preserve performance only 3 of 3+ files are displayed.")
+        end
+      end
+    end
   end
   describe "tags" do