bug#12488: 24.2.50; vc-delete-file and vc-rename-file should default to the current buffer's file

[Chong Yidong]

Dmitry Gutov <dgutov@yandex.ru> writes:

> Do you think I can add commands like `vc-rename-this-file' and
> vc-delete-this-file' instead? And then replace `vc-rename-file' in VC
> menu with the first one and add the second one below it?
>
> Because `vc-rename-file' is likely the only command in that menu that
> acts on a single file, but does't automatically use the one the
> current buffer visits.

I'd rather not have this kind of duplication of commands.  It's more
consistent with other Emacs commands to offer the current file as the
minibuffer default.