The current Vis() and Unvis() are using the C implementation from
MTREE(8).
But that means that cgo is used, which is not always desired.
Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>
Perhaps this is not completely ideal, because it brings in cgo.
And with the flags, it can have tailored experience.
I've added a basic test to ensure that the cases we're interested in are
covered.
This does not yet integrate the usage of Vis()/Unviz() into the manifest
create and compare.
Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>