Merge branch 'stable-3.3'

* stable-3.3:
  Add the configuration for the merge changes grace time
  Introduce change-ts cache for showing changes just merged
  Extract the change cache key to a separate class
  Align open changes cache class name with its name
  Introduce cache for open changes
  Reduce spamming by lowering to debug the invalid changes

Change-Id: I4c5ebf3a3d854cc25bdb91115b751433443655b6