cherries.sh: Check if patch has already been applied.

If the last commit is the same as the patch, do not patch again.
PS2:  download patch silently only once
PS3:  add advisory message
PS4:  LUKASZ ocd kicked in ...
PS5;  Trim advisory message

Change-Id: I171c21acb5da5cae0d2cd4c22d05c17f02717711