Diff CI task fails when force pushing

[saihaj]

@IvanGoncharov not sure why Diff CI task is failing :/

@saihaj Please ignore it, I think it breaks when you force-push stuff.
If you have time to look into it, would be great to fix it.
If not please open an issue so we don't forget to fix it.

Originally posted by @IvanGoncharov in #3269 (comment)