Add core copy detection algorithm
This adds findcopies, which detects merge-relevant copies between
files in a pair of manifests back to the merge ancestor.
While the merge code invokes the copy detection routine, it does not
yet use the result.
#!/bin/sh
mkdir t
cd t
hg init
echo foo > a
echo foo > a2
hg add a a2
hg ci -m "start" -d "0 0"
hg mv a b
hg mv a2 b2
hg ci -m "rename" -d "0 0"
echo "checkout"
hg co 0
echo blahblah > a
echo blahblah > a2
hg mv a2 c2
hg ci -m "modify" -d "0 0"
echo "merge"
hg merge -y --debug
cat a
cat b
hg ci -m "merge" -d "0 0"