New eoan installation, just installed git and vim and recovered one of my projects from backup. Configured git user.email and user.name, made a couple of small changes, tried commit and... nano started. It took me some time to understand how to exit it without committing (BTW I use vim). Neither VISUAL nor EDITOR are set, and the git guide says

By default, Git uses whatever you’ve set as your default text editor via one of the shell environment variables VISUAL or EDITOR, or else falls back to the vi editor to create and edit your commit and tag messages.

(https://git-scm.com/book/en/v2/Customizing-Git-Git-Configuration).

Well, I set EDITOR=vi in my profile, but I'd like to understand what's going on here. Any idea?