Merge branch 'hide-large-diffs' into 'master'

Show a notice for diffs that are empty/too large

This builds upon https://gitlab.com/gitlab-org/gitlab_git/merge_requests/72 but will fail until said MR has been merged.

Fixes gitlab-org/gitlab-ce#13912, gitlab-org/gitlab-ce#13644, gitlab-org/gitlab-ce#13557, gitlab-org/gitlab-ce#13267, gitlab-org/gitlab-ce#3906

See merge request !3185

lib/gitlab/diff/file.rb

@@ -24,6 +24,10 @@ module Gitlab
         @lines ||= parser.parse(raw_diff.each_line).to_a
       end
 
+      def too_large?
+        diff.too_large?
+      end
+
       def highlighted_diff_lines
         Gitlab::Diff::Highlight.new(self).highlight
       end