bug#11809: document "So how do we just simply make a backup file?"

[Jim Meyering]

address@hidden wrote:
> OK but (info "(coreutils) Backup options") should also link back to the exact
> cp -b spot, else most folks will miss it.
>
> P.S., There _is_ an easier way of making backups of several files,
> But there is a bug, one has to do it one at a time despite -b. Bug bug bug.
>
> $ \cp -fb h k l .
> cp: `h' and `./h' are the same file
> cp: `k' and `./k' are the same file
> cp: `l' and `./l' are the same file
> $ \cp -fb h h
> $

No, that was deliberate.

I deliberately restricted the "make backup only" functionality to the
very limited case that is documented.  Widening the semantics, as you
suggest above, seems like it would make this "feature" more likely to
be discovered accidentally -- with data loss, when both originals and
backups are removed.

If people think the make-backup-only feature is useful enough for
multiple files, then we can consider adding an --only-backup option,
(better name welcome, but it cannot start with "--backup") rather than
co-opting the --force --backup combination and requiring a script to
process more than one at a time.