merge: avoid superfluous filemerges when grafting through renames (issue5407)...
merge: avoid superfluous filemerges when grafting through renames (issue5407)
This is a fix for a regression introduced by the patches for issue4028.
The test changes are due to us doing fewer _checkcopies searches now, which
makes some test outputs revert to the pre-issue4028 behavior. That issue itself
remains fixed, we only skip copy tracing for files where it isn't relevant.
As a nice side effect, this makes copy detection much faster when tracing
backwards through lots of renames.
