Confusing diff when changing file encoding

[jpraet]

• Gitea version (or commit ref): 1.15
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (https://try.gitea.io/jpraet/encoding/commit/7d1a5559f40bb2520c42d08c9508c2e5d82d98d5)

Description

I have commits that change the encoding of files from Windows Cp1252 encoding to UTF-8.

In Gitea, the diff makes it look like the special characters get converted incorrectly.

https://try.gitea.io/jpraet/encoding/commit/7d1a5559f40bb2520c42d08c9508c2e5d82d98d5

When viewing the new file, it is displayed correctly as UTF-8 though.

https://try.gitea.io/jpraet/encoding/src/commit/7d1a5559f40bb2520c42d08c9508c2e5d82d98d5/test.txt

On GitHub, it looks like this: jpraet/encoding@7d1a555

Git diff output: