The following case does not terminate:
scheme@(guile-user)> (use-modules (srfi srfi-37))
scheme@(guile-user)> (define opts (list (option '(#\I) #f #t (lambda _ #t))))
scheme@(guile-user)> (args-fold '("-I") opts (lambda _ (error "unrecognized"))
(lambda _ #f) '())
[spins forever](This is an option with a short name, optional argument; it is used without that optional argument.) Ludo’.
