Fix copies reporting in log and convert.
If copy logged in file revision, we report copy for changeset only
if file revisions linkrev points back to the changeset in question
or both changeset parents contain different file revisions.
This fixes extra copies reported when executable bit was changed for
previously copied file.
#!/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