`mv` should preserve hardlinks and allow faster unpack on the same
filesystem. A secondary pass is done with `cp` to copy over attributes
onto any existing directories.
We only run this for nested unpacks as most direct Directory strategy
usage is for repositories where moving files breaks existing code.
This uses `cp -pR` for non-move as some potential user reported issues
could be due to Apple's `cp -l` on specific macOS versions. Can
consider re-adding `cp -l` with better handling for older macOS.
Try running `cp -al` to preserve hardlinks on both macOS and Linux.
If that fails, fall back on `cp -a` which can preserve hardlinks on
Linux (but not macOS) assuming target filesystem supports them.
