bug#55267: 29.0.50; Provide customization to save project-find-file arg to savehist

[Juri Linkov]

> I just noticed that "project-find-file" is ultimately calling
> "find-file" only. So it should save the file to minibuffer history if
> savehist-mode is enabled.
>
> But this is not happening in my environment right now. Is this a bug
> (instead of feature request)?

Recently I noticed this problem too.  So project-find-file-in
needs to specify the same history variable 'file-name-history'
as used in read-file-name-default.

Then you could add 'file-name-history' to savehist-additional-variables.