>Additional change is that it uses symlink() rather than link().
I don't think this is going to work for use in practice. When updating a
certificate what uacme does is
create a new-crt.pem and new-key.pem
hardlink the existing key.pem to timestamped-key.pem
hardlink the existing crt.pem to timestamped-crt.pem
unlink key.pem
unlink crt.pem
rename new-crt.pem to crt.pem
rename new-key.pem to key.pem
With a symlink timestamped-key.pem will not contain the the content of
key.pem, so there will be no useful backup. The is why is suggested that
the link needed to be replaced with a copy operation.