Enabling vc commands when visiting a remote file via Tramp?

[Skip Montanaro <skip.montanaro@gmail.com>]

I'm doing development in a docker environment, and find it handy to
just visit files using Tramp instead of starting up a second Emacs
instance on my Docker machine (which is not my normal machine - not my
choice, nothing I can do about it). This works fine for the most part
(proper modes are displayed, for example), and the difference between
explicitly visiting a remote file (Tramp) vs implicitly visiting that
same file (NFS) isn't worth worrying about.

Still,  version control detection and support appears to be
nonexistent by default. I see that vc-ignore-dir-regexp is set to some
inscrutable regular expression. That might, or might not, be the key.
Is there a known setting of that variable which will unlock the magic
of vc through Tramp?

Thx,

Skip Montanaro