ivy.el (ivy--reset-state): Filter sorted alist

[basil-conto]

Fixes #1705

I've also simplified the surrounding code a bit in the subsequent two commits.

[abo-abo]

Could you please resolve the merge conflict?

[basil-conto]

Could you please resolve the merge conflict?

Done, thanks.

[abo-abo]

Please be careful about removing copy-sequence. In all likelihood, there's a purpose for them:

;; oops:
(let ((coll '(("b" . "1") ("a" . "2"))))
  (ivy-with '(ivy-read "test:" coll
              :sort t)
            "C-m")
  coll)
;; => ((#("b" 0 1 (idx 1)) . "1"))

[basil-conto]

Please be careful about removing copy-sequence.

I was, but clearly not enough. I was expecting cl-remove-if-not to allocate a new sequence, but I see now that it only does that on demand, which I don't think makes sense in the presence of cl-delete-if-not.

[basil-conto]

Wow, cl-remove behaves totally differently to remove:

(let* ((seq (list 1 2 3))
       (sub (cl-remove 1 seq)))
  (setcar sub 5)
  seq) ; => (1 5 3)

I wonder if this is intentional or a bug.

[basil-conto]

In any case, I've re-added the copy-sequence.

[abo-abo]

Thanks.