vfs: extract the audit path logic into a submethod This will make it possible to apply it in more cases.

subrepo-git: use an official origvfs when appropriate The origvfs has the auditor properly set and can move file without issue. The current code is currently working without errors because rename are not audited, yet.

revert: extract origvfs logic in a sub-function The subrepo's "revert" logic could benefit from it.