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
hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'
hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'
hg debugrename foo
hg debugindex .hg/store/data/bar.i