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

[Thierry Volpiatto <thierry.volpiatto@gmail.com>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> Ok, that is true for the solutions you propose below, but what's wrong
>> with the solution I have proposed:
>> Just checking if the destination directory is a subdirectory of the
>> directory we want to copy.
>
> It's not a bad plan, but it's difficult to make it catch all cases
> because it's difficult to figure out if "the destination directory is
> a subdirectory of the directory we want to copy".
> [ e.g. because of ignored cases differences, or use of different names
>   to refer to the same directory, because of MICROS~1 mangling.  ]
The function I sent works also on Windos, but yes maybe there is cases
where it doesn't work, don't know.
Would be nice if somebody find some use cases where it fails on windows.

> Of course checking if two directories are one and the same isn't that
> easy to do it reliably either (e.g. for lack of inodes on Windows
> systems, and actually I'm not sure what happens if we refer to the same
> dir via two different mount points, using GNU/Linux's "bind" mounts, or
> mounting dirs multiple times).
Hmm, didn't try that, recipe welcome.

> I guess the two options aren't mutually exclusive, so it's probably
> worth doing a first check before starting the whole operation (trying
> to find out if the destination is a parent of the source based on
> file-truename), and then adding another check in the recursive loop to
> try and detect inf-loops.
That seem good option, so actually only code to detect inf-loops is
missing to achieve that?

-- 
  Thierry
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