See the cross-post cover letter for details:
https://www.redhat.com/archives/libguestfs/2019-August/msg00322.html
Eric Blake (1):
  protocol: Add NBD_CMD_FLAG_FAST_ZERO
 doc/proto.md | 50 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)
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2.21.0