class Gem::Tasks::SCM::Tag

def sign?
  if @sign.nil?
    @sign = case @project.scm
            when :git
              !`git config user.signingkey`.chomp.empty?
            when :hg
              !`hg showconfig extensions hgext gpg`.chomp.empty?
            else
              false
            end
  end
  return @sign
end