Eli Zaretskii <eliz@gnu.org> writes:

>> From: npostavs@users.sourceforge.net
>> Cc: 16984@debbugs.gnu.org,  Eli Zaretskii <eliz@gnu.org>,  jidanni@jidanni.org
>> Date: Thu, 08 Dec 2016 09:39:35 -0500
>> 
>>     (defun minibuffer-maybe-quote-filename (filename)
>>       "Protect FILENAME from `substitute-in-file-name', as needed.
>>     Useful to give the user default values that won't be substituted."
>>       (let ((local (file-remote-p filename 'localname)))
>>         (if (and (not (string-prefix-p "/:" local))
>>                  (file-name-absolute-p filename)
>>                  (string-match-p "/~" local))
>>             (tramp-quote-name filename)
>>           (minibuffer--double-dollars filename))))
>
> Is the argument guaranteed to come from expand-file-name?  If not, it
> should also accept file names matching "\~" on MS platforms.

I think it does, but I'm not entirely sure.  Better safe than sorry?