open("C:/Users/peipei/Desktop/svn2.diff", 'w') do |f|
    open("C:/Users/peipei/Desktop/svn.diff", 'r') do |ff|
        ff.readlines.each do |line|
            if line.start_with?("@@")
                line =~ /@@\ \-(.+)\ \+(.+)\ @@/
                f << "@@\ \-#{$2}\ \+#{$1}\ @@\n"
            elsif line.start_with?("+ ")
                f << "-#{line.slice(1..-1)}"
            elsif line.start_with?("- ")
                f << "+#{line.slice(1..-1)}"
            else
                f << line
            end
        end
    end
end