Add Version field to ContentChange

Add Version field to ContentChange

As discussed on IRC. One notable consequence is that the ContentWatcher now
fires on version changes that don't involve a content change; this is not
a big deal, because we shouldn't be writing to nodes in the first place if
their state has not changed; and if that does ever happen the only result
should be to reestablish some state that was in fact already established.

https://code.launchpad.net/~fwereade/juju-core/watch-content-versions/+merge/111811

(do not edit description out of merge proposal)

[fwereade, 2012-06-25 10:41:59]

Please take a look.

[fwereade, 2012-06-27 15:10:24]

Please take a look.

[niemeyer, 2012-06-28 06:21:29]

LGTM

https://codereview.appspot.com/6330053/diff/5001/state/watcher/watcher.go
File state/watcher/watcher.go (right):

https://codereview.appspot.com/6330053/diff/5001/state/watcher/watcher.go#new...
state/watcher/watcher.go:11: // valid when Exists is true.
// ... Version and Content will be zeroed
// when Exists is false.

[fwereade, 2012-06-28 07:37:15]

*** Submitted:

Add Version field to ContentChange

As discussed on IRC. One notable consequence is that the ContentWatcher now
fires on version changes that don't involve a content change; this is not
a big deal, because we shouldn't be writing to nodes in the first place if
their state has not changed; and if that does ever happen the only result
should be to reestablish some state that was in fact already established.

R=niemeyer
CC=
https://codereview.appspot.com/6330053

https://codereview.appspot.com/6330053/diff/5001/state/watcher/watcher.go
File state/watcher/watcher.go (right):

https://codereview.appspot.com/6330053/diff/5001/state/watcher/watcher.go#new...
state/watcher/watcher.go:11: // valid when Exists is true.
On 2012/06/28 06:21:30, niemeyer wrote:
> // ... Version and Content will be zeroed
> // when Exists is false.

Done.