gistfile1.lua

for s = 1, screen.count() do
    awful.tag.attached_add_signal(s, "property::selected", function(tag)
        local idx = nil
        for i, v in pairs(screen[s]:tags()) do
            if v == tag then
                idx = i
                break
            end
        end
        if not idx then return end

        for x = 1, screen.count() do
            if x ~= s then
                awful.tag.viewonly(screen[x]:tags()[idx])
            end
        end
    end)
end