When the current editor is diff/blame/whatever and not a file, the "current file" for VCS operations is the file that was active before that editor was opened. This is confusing.

I just accidently reverted all my changes to a file because of that. I opened a diff for a certain file (from the commit editor), then I wanted to revert it, so in the diff editor I did Git -> "Undo uncommitted...", and it reverted another file...