pub fn share_cards() -> Result<(), String>Expand description
What your other devices learn of your security keys, written from this
device’s own (cards.toml, and their certificates kept with your keys):
only the keys this device read itself, never one it learnt from another
device. Each certificate merged with the one shared already, so that a
renewal made on another computer is never undone. A file is written only
when what it says changed. Keys this device does not know are left as
they are (another computer’s).