Fix bug #345. The last hit for a file might have been before the last window, so we can't clear copies. To reduce the load, we only store real copy entries instead of storing hashes for every revision.

#!/bin/sh

mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m "test" -d "1000000 0"
hg verify
hg parents
hg status
hg rollback
hg verify
hg parents
hg status