bug#30285: dired-do-chmod vs. top line of dired

[Tino Calancha]

On Tue, 30 Jan 2018, Drew Adams wrote:

> Obviously, for `dired-do-*' commands we still need to
> handle the case where files or dirs are marked.  And
> in that case the command should DTRT even if called from
> a non-file line, i.e., one of the problematic places
> we've been discussing - it should not raise an error
> in that context.
IIRC, my latest patch handle those situations pretty well.
Could you tested it and provide feedback about how to
improve it?

> For `dired-do-*' commands that already call
> `dired-get-marked-files' the clear solution, I think,
> is to just test that return value and raise an error
> if it is nil.
>
> If there is are `dired-do-*' commands that do not call
> `dired-get-marked-files' then we have a choice how to
> solve the problem.  But it might well be that even then
> the best solution is to use `dired-get-marked-files'.
Since you are reluctant to the addition of the new predicate.  That's 
fine.
May I ask you to provide an alternative  patch to compare
with mine? Then, people here might do further feedback based
on those 2 alternatives.

Thank you very much!