Re: [found the culprit]

[Stefan Monnier]

> I just mentioned what it uses, and has used for a
> long time.  And it's a general scheme, applied to `dired-do-*'
> commands generally.  The conflict is not a minor one, e.g.,
> affecting just `Z'.

FWIW, I don't think it's a good scheme.  Better would have
more mark-management commands that you can then combine with any
dired command without having to fight with conflicting uses of C-u.
E.g. commands to "push" and "pop" the current set of marked files,
and a command that you can iterate like your C-u which will first mark
the current file, then the files in the current directory, then ...
A nice advantage to C-u is that these would give you visual feedback
about which files are selected.

> 2. How does the above C-u usage "not follow Emacs's use of C-u"?

Emacs usually does not use multiple C-u and also tries to avoid
distinguishing between "just C-u" and "a numeric argument".  There are
exceptions to both of those "rules", and I'm to blame for some of those
exceptions, but I think this case is not a good candidate for an
exception because there are too many "sets of files" that the user might
like to specify, so we'll be better served by providing this separately
than trying to cleverly cram some common cases into the narrow C-u.


        Stefan