How to cache GPG passphrase

/usr/bin/gpg-agent --daemon --allow-preset-passphrase

/usr/lib/gnupg/gpg-preset-passphrase -c KEYGRIP  -P 'YOUR_PASSPHRASE'

KEYGRIP can be found like this:

gpg --edit-key EMAIL_OF_YOUR_KEY

grip

quit

Use pub key Keygrip.

DEBUG:

/usr/bin/gpg-agent -vv --daemon --allow-preset-passphrase --debug-level 9

/usr/lib/gnupg/gpg-preset-passphrase -v -c KEYGRIP -P 'YOUR_PASSPHRASE'