@matthiasmullie I seem to remember that the reason you wanted to fix this was it caused some kind of bug - it looked liked you'd be able to upload a file that has the same name as a file on a remote repo, but at the last minute you get blocked ... something like that anyway. I can't remember for sure, can you remind me so I can take a look at it?

The problem is that it will *not* error or warn.

Reproduce:
1/ Download a random file from commonswiki (e.g. https://commons.wikimedia.org/wiki/File:HamptonCourtHerefordshire.jpg)
2/ Make a copy of that file & rename it (so that you have 1 copy with the original name, and one with a name that does not already exist)
3/ Attempt to upload both files to testwiki: https://test.wikipedia.org/wiki/Special:UploadWizard or https://test.wikipedia.org/wiki/Special:Upload
4/ Notice how the renamed copy will show a warning ("This file is a duplicate of the following files: File:HamptonCourtHerefordshire.jpg" and will allow you to "Upload anyway"), but the one with the original name will not show any warnings

The renamed version is ok: you're informed that the file already exists in a remote repository, but it'll still let you upload it if you so desire.

The original name will not give such warning.
When you continue uploading, you'll eventually be warned about using the same filename as an existing file ("A file with this name exists already. If you want to replace it, go to the page for File:HamptonCourtHerefordshire.jpg and replace it there."), but you can just rename it and keep uploading, without having been informed that the *content* of the file also exists already.

Change 394351 had a related patch set uploaded (by Cparle; owner: Cparle):
[mediawiki/core@master] Warn for uploads with new name but same content as local file

https://gerrit.wikimedia.org/r/394351

Change 394351 merged by jenkins-bot:
[mediawiki/core@master] Warn for uploads with new name but same content as local file

https://gerrit.wikimedia.org/r/394351