add an exclamation mark to the commandlines: gpg --sign -u "xxx!"

I have my master private key on a different smart card than the sub keys I use day by day. Eventhough the specific key is specified, the sign operation can fail, if gpg tries the wrong one first.
It is easily solveable py adding an exclamation mark:

not working for me :
gpg -u 'b51ba150670f5adf47f34f4cdcc6e50f0ae275a9' -a --sign

works:
gpg -u 'b51ba150670f5adf47f34f4cdcc6e50f0ae275a9!' -a --sign

Start by locating the command-line handling for signing and inspect how the -u option is passed to gpg. Reproduce the two commands from the issue with keys on separate smart cards. Done means the requested key can be selected reliably using the exclamation-mark form.

Written by the indexing model from the issue text.