def has_sign_off?(commit_or_message)
      message = commit_or_message.is_a?(String) ? commit_or_message : commit_or_message.message
      if message =~ /^Signed-off-by: (.+)$/
        $1
      else
        nil
      end
    end
def has_sign_off?(commit_or_message)
      message = commit_or_message.is_a?(String) ? commit_or_message : commit_or_message.message
      if message =~ /^Signed-off-by: (.+)$/
        $1
      else
        nil
      end
    end
Check if a commit or commit message is already signed off.

 @api private
 @param commit_or_message [String, Git::Commit] Commit object or message string.
 @return [String, nil]