bug#10489: 24.0.92; dired-do-copy may create infinite directory hierarchy

[Thierry Volpiatto]

Michael Albinus <michael.albinus@gmx.de> writes:

> Thierry Volpiatto <thierry.volpiatto@gmail.com> writes:
>
>> The last patch use this instead, which avoid duplication of code and is
>> more readable.
>>
>> (defun files-copyable-p (from to)
>>   "Verify if file FROM is not the same than TO on this system."
>>   (let* ((fromname     (file-name-as-directory (file-truename from)))
>>          (destname     (file-name-as-directory (file-truename to)))
>>          (rem-fromname (and (equal "sudo" (file-remote-p fromname 'method))
>>                             (string-match (system-name)
>>                                           (file-remote-p fromname 'host))
>>                             (file-remote-p fromname 'localname)))
>>          (rem-newname  (and (equal "sudo" (file-remote-p destname 'method))
>>                             (string-match (system-name) (file-remote-p 
>> destname 'host))
>>                             (file-remote-p destname 'localname))))
>>     (not (equal (or rem-fromname fromname)
>>                 (or rem-newname destname)))))
>
> Again, Thierry: it is the wrong approach, to implement such logic in
> files.el (or another package not related to remote files). You do not
> know all details of the packages handling it. In this example, you have
> handled "/sudo:", but you haven't handled "/su:". And other missing
> details.
Ok

> And you have called `file-truename' before comparing, whether the
> "remoteness" of the files are equal. This is a performance issue,
> because `file-truename' will always do expansive remote operations, even
> if `from' and `to' are located on different hosts, and there is no
> reason to find out their respective true names.
Ok 

> You are invited to implement `tramp-handle-file-eual-p', once
> `file-equal-p' is added for Emacs 24.2. For the time being (Emacs 24.1),
> it is sufficient to compare the result of `file-remote-p' as Drew has
> shown in the example.
Many examples given here, so if everybody is ok with The function given
by Drew, we could commit the attached patch to fix this bug:

-- 
  Thierry
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