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

[Stefan Monnier]

>> read-file-name-completion-ignore-case is a user configuration which only
>> reflects the underlying system's sensitivity by default but the user is
>> free to modify it.  I used to set it to t under GNU/Linux, for instance.
> (eval (car (get 'read-file-name-completion-ignore-case 'standard-value)))
> would do, but that's too hackish ??

Yuck.  I'd much rather introduce a new defconst which is then used to
provide the default value of read-file-name-completion-ignore-case.

BTW, a reliable test of file name equality is far from obvious.  E.g.
"/ssh:toto:/titi" is equal to "/ssh:TOTO:/titi" but whether
"/ssh:toto:/titi" is not equal to "/ssh:toto:/TITI" if titi
is a typical GNU/Linux machine.


        Stefan