"show --show-signature" and "log --show-signature" do not read the
gpg.program setting from git config, even though, commit signing,
tag signing, and tag verification honor it.
Signed-off-by: Jacob Sarvis <jsarvis@openspan.com> Signed-off-by: Hans Brigman <hbrigman@openspan.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>