--sync-watermark: don't allow subtree wm get above upstream wm
--sync-watermark: don't allow subtree wm get above upstream wm

In case root is lagging, the subtree should not drop events.

overdrive3000/skytools,tarvip/skytools,tarvip/skytools,overdrive3000/skytools,overdrive3000/skytools,markokr/skytools,tarvip/skytools,markokr/skytools,markokr/skytools