bug#65348: INITIAL-INPUT in completing-read repeats same entry twice consecutively

[Drew Adams]

> > > Would it not be better to COLLECTION and HISTORY separate ?
> >
> > You already have my opinion: yes. And they always
> > have been, till Someone (TM) decided recently that
> > future history should include all of the candidates
> > in COLLECTION.
> 
> Right.  Because entries in history ought to be stored in history
> as you input values, not before.

Not so, for "future history" (and that's why that cute
term isn't a good one).  The so-called "future history"
is one or more DEFAULT values you can retrieve and use
as input if you like.

After use of DEFAULT (`M-n') got rebaptized as using
"future history", Someone (TM) got the dim idea to add
all of COLLECTION to that list, along with the DEFAULT
values.  DEFAULT values belong, properly, to "future
history" (though that's a misleading misnomer).

But COLLECTION doesn't belong in "future history".
The reason isn't what you gave, though.  It's proper
to fill the "future history" before you choose input,
but it's only proper to fill it with default values.
What's not good is to also fill it with all of the
possible completion choices.