localrepo: changed revs to use spanset instead of baseset
Performance benchmarking:
$ time hg log -qf -l1
...
real 0m1.420s
user 0m1.249s
sys 0m0.167s
$ time ~/local/hg/hg log -qf -l1
...
real 0m0.719s
user 0m0.614s
sys 0m0.103s
% creating repo% add and commitC test.py% changeM test.py