If using Linux 6.9 or above and enabled (passthrough=true) files
opened or created will use the FUSE passthrough feature.
If direct-io=true / cache.files=off it will override passthrough. If
direct-io-allow-mmap is enabled only mmap will passthrough.
HANDLE_KILLPRIV and V2 are enabled now by default to remove the
kernel's need to issue getattr and getxattr requests.
moveonenospc will not work when leveraging passthrough.
* follow-symlinks: allows mergerfs to transparently follow symlinks
* link-exdev: in the event a link returns EXDEV create a symlink instead
* rename-exdev: in the event a rename returns EXDEV move the oldpath and
create a symlink for the newpath
