[sheepdog] [sheepdog/sheepdog] ab458c: add -d option for dog cluster info

[Meng Lingkun]

  Branch: refs/heads/master
  Home:   https://github.com/sheepdog/sheepdog
  Commit: ab458ca316fecbe0a95befd6454ecdd33c70e892
      https://github.com/sheepdog/sheepdog/commit/ab458ca316fecbe0a95befd6454ecdd33c70e892
  Author: Meng Lingkun <menglingkun at cmss.chinamobile.com>
  Date:   2015-08-27 (Thu, 27 Aug 2015)

  Changed paths:
    M dog/cluster.c

  Log Message:
  -----------
  add -d option for dog cluster info

Dog cluster info with option -d just outputs the changed nodes
between the two adjacent epoches. It's useful in a cluster with
a large amount of nodes. And it would be a way easier to create
a nagios/icinga script that advertises you when something changes
in the cluster and what has changed.

Signed-off-by: Meng Lingkun <menglingkun at cmss.chinamobile.com>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>