Patch: Lazy wdired preprocessing

[Arthur Miller]

The original thread seems to have become more of a lisp language thread,
so to make it easier, I made a new one, with more descriptive name.

Attached is new a version of patch. Seems to correctly work with
permissions now. I have also discovered (current-column) function so I
no longer calculate columns in my own code :-).

I have tested on my ext4 file system where my normal system is
installed, and there it works correctly.

I have also tested on one NTFS drive, where I can not change permissions
normally and there is following behaviour, don't know if it is
acceptable or not:

In wdired buffer I can seemingly change permission, but when I save
buffer, then permission is of course not saved and reverted dired buffer
shows correct permission. In Dolphin, it seems to work similar (I can
set pulldown menu in permissions dialog to only read, and press OK, but
it is not saved).

There is also a question what happeneds when one have an empty folder
and switches to wdired buffer. I don't see it handled in old wdired, so
I have added an error condition for that in
wdired-change-to-wdired-mode.

Please test it, there might be some other test condition I haven't
tested. I am attaching both the working file for easy evaluation and
test, and the patch.

best regards
/a

0001-Lazy-wdired-preprocessing.patch
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lazy-wdired.el
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