macOS macfuse has an extra options parameter for the setxattr and
getxattr FUSE callbacks. The possible options are documented below.
However the underlying libguestfs APIs don't allow us to act on these
flags, so we ignore them for now.
(from https://manp.gs/mac/2/setxattr)
XATTR_NOFOLLOW
do not follow symbolic links. setxattr() normally sets attributes
on the target of path if it is a symbolic link. With this option,
setxattr() will act on the link itself.
XATTR_NOFOLLOW_ANY
do not follow any symbolic links encountered during pathname
resolution. An error is returned if a symlink is encountered
before the last component of path.
XATTR_CREATE
fail if the named attribute already exists.
XATTR_REPLACE
fail if the named attribute does not exist. Failure to specify
XATTR_REPLACE or XATTR_CREATE allows creation and replacement.
Reported-by: Mohamed Akram
Fixes: https://github.com/libguestfs/libguestfs/issues/180
Related: https://github.com/macfuse/macfuse/issues/1065
63a2ed92b4