Show un-highlighted diffs when blobs are the same

For some old merge requests, we don't have enough information to figure out the
old blob and the new blob for the file. This means that we can't highlight the
diff correctly, but we can still display it without highlighting.

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/gitlab/diff/file.rb b/lib/gitlab/diff/file.rb
index 17a9ec01637..1dabd4ebdd0 100644
--- a/lib/gitlab/diff/file.rb
+++ b/lib/gitlab/diff/file.rb
@@ -186,7 +186,10 @@ module Gitlab
       end
 
       def content_changed?
-        old_blob && new_blob && old_blob.id != new_blob.id
+        return blobs_changed? if diff_refs
+        return false if new_file? || deleted_file? || renamed_file?
+
+        text? && diff_lines.any?
       end
 
       def different_type?
@@ -225,6 +228,10 @@ module Gitlab
 
       private
 
+      def blobs_changed?
+        old_blob && new_blob && old_blob.id != new_blob.id
+      end
+
       def simple_viewer_class
         return DiffViewer::NotDiffable unless diffable?