Suggestion needed: fix T3416 gpg should select available signing key on card (even with -u option)

[NIIBE Yutaka]

Frederick Zhang via Gnupg-devel <gnupg-devel at gnupg.org> wrote:
> I encountered the issue of T3416 gpg should select available signing key
> on card (even with -u option) <https://dev.gnupg.org/T3416> recently and
> I've been working on a fix for it. But since I've got little knowledge
> about GPG internals, it'd be nice if I can have some feedback and
> suggestions from you and maybe get the changes merged if they do make
> sense :)

Please describe your problem, what you need/want, what to be achieved,
etc., at first.  It is more helpful than a patch.

In my opinion, your approach of changing key search algorithm
(finish_lookup) looks not good, because the impact is larger.
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