I was trying to sign my commits with the command git commit -S but it fails without prompting my passphrase for my GPG key.
The error is:
error: gpg failed to sign the data
fatal: failed to write commit object
I noticed that if I run the following command before git commit -S:
gpg -o /dev/null --local-user MY_KEY_ID -as <(echo 1234) && echo "The correct passphrase was entered for this key"
...everything works well and my commits are properly signed. I think it's because my passphrase is cached but this is not the behaviour that I expect.
I was hoping that Git would prompt for my passphrase everytime I want to sign commits or tags.
The command to "unlock my key" was found on this question: How to use gpg command-line to check passphrase is correct
You likely need to tell pinentry, the software gpg uses to prompt for your password, where to prompt you.
export GPG_TTY=$(tty)
git commit -S
If this works I would recommend exporting GPG_TTY in your shell's 'rc' file.