When online-editing a file with @ (at) in the name a new file created with `%40` instead

Steps to reproduce:

1. Add a file with @ in ints name to the repo, e.g. foo@bar.
2. Edit it online.
3. Commit.

Expected result: the file is updated.

Actual result: a new file – foo%40bar is added to the repo; a default commit message also mentions the wrong name.