[stellation-res] Checkin: fix of NCA bug

["Mark C. Chu-Carroll" <mcc@xxxxxxxxxxxxxx>]

I just checked in a change that seems to fix the nearestCommonAncestor
bug recently reported. 

One odd thing is that this change sometimes passes script test 14, and
sometimes fails. No clue about why yet, but I thought it was worth
checking in, since everything else passes fine.

I also checked in a new unit test suite, StandaloneHistoryTest, which
tests nearestCommonAncestor computation. The tests come from an XML test
spec file, which currently only contains four tests that specifically
target the bug I was fixing. I'll be extending this suite to cover many
more tests as I have time.

	-Mark

-- 
Mark Craig Chu-Carroll,  IBM T.J. Watson Research Center  
*** The Stellation project: Advanced SCM for Collaboration
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