[MERGE][1.0] Fixes for find_differences() and get_parents_map()

[John Arbash Meinel]

John Arbash Meinel has voted resubmit.
Status is now: Resubmit
Comment:
There was some follow up work done to make find_differences properly 
spider. In doing so, the performance dropped down into approximately 
"search all the graph all the time". More investigation is needed to 
sort out if there is really a way to make a fast find_differences that 
is still correct.

See: https://bugs.launchpad.net/bzr/+bug/187452 for any follow up work.


For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C475B50C1.3020909%40arbash-meinel.com%3E