If a commit includes rename operations, the new filename is shown in History → commit file list at the bottom left, next to the "R" icon.
How can I see the old filename? (A 2014 Jira issue stated, "From the next version the header of the diff pane will have a tooltip which provides this information", but selecting the file and hovering over the diff pane's header has no effect. Running Windows 3.1.2.)