Set up Fish Shell to use gpg-agent as the SSH agent for Yubikeys and other smart cards

config.fish

# Add these contents to ~/.config/fish/config.fish
# If using Brew, config.fish is located in /usr/local/Cellar/fish/[version]/etc/fish/
# Generally recommend using the installer from https://fishshell.com instead of brew
# to avoid version updates overwriting the config file

# Start or re-use a gpg-agent.
gpgconf --launch gpg-agent

# Ensure that GPG Agent is used as the SSH agent
set -e SSH_AUTH_SOCK
set -U -x SSH_AUTH_SOCK ~/.gnupg/S.gpg-agent.ssh

# Credit and more info: https://rnorth.org/easier-ssh-agent-with-gpg