bug#59384: 29.0.50; Visiting files in Emacs Git pops up "unsafe variable" prompt

[Juri Linkov]

>       vc-git-annotate-switches : "-w"
>       bug-reference-url-format : "https://debbugs.gnu.org/%s";
>       diff-add-log-use-relative-names : t
>     * vc-prepare-patches-separately : nil
>       c-file-style : "GNU"
>       c-noise-macro-names : ("INLINE" "NO_INLINE" 
> "ATTRIBUTE_NO_SANITIZE_UNDEFINED" "UNINIT" "CALLBACK" "ALIGN_STACK")
>       electric-quote-comment : nil
>       electric-quote-string : nil
>       indent-tabs-mode : t
>       mode : bug-reference-prog
>
> The problem here AFAIU is that vc-prepare-patches-separately and its
> 'safep' property is not known to Emacs until vc.el is loaded.
>
> One way of fixing this would be to autoload the defcustom of this
> variable, but AFAIR this is sometimes frowned upon?

Is there a standard solution already worked out for existing
variables like `vc-git-annotate-switches'?