I have added this option to my
gpgsign = true
gpg: gpg-agent is not available in this session
As mention here, that might be because
gpg-agent --version and
gpg --version differ.
$PATH: you might find a gpg.exe in one folder, and a
gpg-agent in another.
Plus, gpg-agent should work with gpg2, and you are using gpg 1...
See "how to install gpg on cygwin? currently it's missing".