Certain URLs to diffs do not redirect on mobile devices.
Expected: User sees Special:MobileDiff
Actual: User sees desktop diff page.
= Acceptance criteria
 When title is specified in the URL e.g. [[ https://de.wikipedia.org/w/index.php?title=Skull&diff=164584307 | example url ]] a redirect occurs taking the user to [[ https://de.wikipedia.org/wiki/Special:MobileDiff/164584307 | the mobile url ]].
= Case 1: Where title is specified in query string
View https://de.wikipedia.org/w/index.php?title=Skull&diff=164584307 on a mobile device (or emulated Chrome Nexus 5)
Expected: user should be redirected to mobile site.
= Case 2: where 2 revisions are specified
Steps to reproduce:
# Go to any page on wiki
# Edit page and add external link like this:
[https://cs.wikipedia.org/w/index.php?title=MyPage&diff=14286854&oldid=14265839 My Page last change]
# Save and open the page in mobile view (mobile web)
# Tap the newly created link
Link redirects to mobile view diff automatically.
Link opens desktop view diff instead.