bug#22894: 25.1.50; dired-mark: Not remark a marked file

[Drew Adams <drew.adams@oracle.com>]

Hi Tino,

> What i am trying to prevent is related with `dired-mark' and
> `dired-mark-files-in-region'. The former is bound to 'm'. I can
> imagine someone, keeping push the 'm' button to mark a bunch of files,
> and releasing such button one fraction of seocnd late, so one marked
> file with 'F' get remarked by `dired-marker-char'.
> Similar thing could happen if using the second function setting the
> region not very carefully (pick uping one additional file up/down
> in the region).
> 
> The patch just prevent in this two function, one marked file be
> remarked. Those files still not marked are marked.

Doesn't sound like a great idea, to me.  At most it should be
optional behavior: a user choice.

Novice users, whom one could think might benefit most from this
protection, will not benefit from it, because they are not likely
to have changed marks.

(In my experience, very few people are even aware of the ability
to change marks, and this is true even of people who have been
developing and maintaining Emacs.)

> I am against to restrict users, and i understand this thread is
> controversial, but i use a lot these features and i believe it
> could prevent people (including me) doing unintentional changes.

But also intentional changes.  Users who know about and use the
ability to change marks should be able to mark over changed marks
with `*', including with `m' and using the region.

You say that you have been using this feature for a while and
appreciate it.  That is the best argument for it, I guess.

If this behavior is optional then it is OK, but I don't see a
great use case for it.  And you mention undo, which also argues
against this.