Regression in support of -- in options

src cat <revision> -- <filename> is used in vc.el in emacs to cat that revision but:

$ src cat 3280 -- todo.org
src: -- is not registered
$ src version
src: 1.39
python: 3.12.4
RCS: 5.10.1
platform: linux

... a regression from #6 (closed) from 5 years ago?