[Libguestfs] [PATCH nbdkit] New tmpdisk plugin.

[Richard W.M. Jones]

Unfinished (needs tests).  This is my attempt to make a
"remote tmpfs" plugin as outlined in this prior email:

https://www.redhat.com/archives/libguestfs/2020-March/msg00134.html

Although it would be possible to construct something a bit like this
using existing plugins and filters (perhaps with some new features in
those filters) I think it may be nicer to have a dedicated plugin for
this, as it makes the documentation simpler to understand and allows
us to implement unique features.  In particular notice that this
plugin only deals with temporary disks so deliberately ignores
flush/FUA, which should make it nice and fast.

Rich.