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

hg init a
echo a > a/a
hg --cwd a ci -A -m a
hg clone a b
echo b > b/b
hg --cwd b ci -A -m b
chmod 100 a/.hg
hg --cwd b push ../a
chmod 700 a/.hg