Add local options lxc-clone and lxc-clone-aufs

Add local options lxc-clone and lxc-clone-aufs

These new values default to the existing behaviour.
That being that if the user is on trusty or above,
they default to true, otherwise false.

The reason for these values is two-fold. Firstly,
aufs isn't working on power, and we want to be able
to test effectively there. Secondly this gives the
user on saucy the ability to try it out (not originally
planned, but a helpful side effect).

https://code.launchpad.net/~thumper/juju-core/local-lxc-clone-settings/+merge/211237

(do not edit description out of merge proposal)

[thumper, 2014-03-17 02:41:42]

Please take a look.

[wallyworld, 2014-03-17 03:08:51]

A few initial questions in the comments.
Also, now that there are config options for clone, doesn't that mean we can now
drop JUJU_TESTING_LXC_FORCE_SLOW, since we can just use config with
lxc-clone=false?

https://codereview.appspot.com/74660044/diff/1/cmd/juju/help_topics.go
File cmd/juju/help_topics.go (right):

https://codereview.appspot.com/74660044/diff/1/cmd/juju/help_topics.go#newcode86
cmd/juju/help_topics.go:86: You can override the clone use by specifying
... the use of clone...

https://codereview.appspot.com/74660044/diff/1/cmd/juju/help_topics.go#newcode90
cmd/juju/help_topics.go:90: in the environments.yaml file for the local block. 
If you have the main
They may not have called their local provider "local", or they may have more
than one defined. I'd just say "in the configuration for your local provider".

https://codereview.appspot.com/74660044/diff/1/container/lxc/lxc.go
File container/lxc/lxc.go (right):

https://codereview.appspot.com/74660044/diff/1/container/lxc/lxc.go#newcode165
container/lxc/lxc.go:165: if manager.backingFilesystem == Btrfs ||
manager.useAUFS {
This logic looks different that what was there before? We are adding an extra
"manager.backingFilesystem == Btrfs" check?

https://codereview.appspot.com/74660044/diff/1/provider/local/config.go
File provider/local/config.go (right):

https://codereview.appspot.com/74660044/diff/1/provider/local/config.go#newco...
provider/local/config.go:29: "lxc-clone-aufs": schema.String(),
why not schema.Bool()?
(used with schema.Defaults to ensure default is true)

https://codereview.appspot.com/74660044/diff/1/provider/local/config.go#newco...
provider/local/config.go:110: func (c *environConfig) lxcClone() string {
so this would return bool as per previous comment

https://codereview.appspot.com/74660044/diff/1/provider/local/config.go#newco...
provider/local/config.go:115: func (c *environConfig) lxcCloneAUFS() string {
ditto

[thumper, 2014-03-17 03:51:39]

Please take a look.

https://codereview.appspot.com/74660044/diff/1/cmd/juju/help_topics.go
File cmd/juju/help_topics.go (right):

https://codereview.appspot.com/74660044/diff/1/cmd/juju/help_topics.go#newcode86
cmd/juju/help_topics.go:86: You can override the clone use by specifying
On 2014/03/17 03:08:52, wallyworld wrote:
> ... the use of clone...

Done.

https://codereview.appspot.com/74660044/diff/1/cmd/juju/help_topics.go#newcode90
cmd/juju/help_topics.go:90: in the environments.yaml file for the local block. 
If you have the main
On 2014/03/17 03:08:52, wallyworld wrote:
> They may not have called their local provider "local", or they may have more
> than one defined. I'd just say "in the configuration for your local provider".

Done.

https://codereview.appspot.com/74660044/diff/1/container/lxc/lxc.go
File container/lxc/lxc.go (right):

https://codereview.appspot.com/74660044/diff/1/container/lxc/lxc.go#newcode165
container/lxc/lxc.go:165: if manager.backingFilesystem == Btrfs ||
manager.useAUFS {
On 2014/03/17 03:08:52, wallyworld wrote:
> This logic looks different that what was there before? We are adding an extra
> "manager.backingFilesystem == Btrfs" check?

What was there before was related to the second check below where
we now also check that the manager has useAUFS as true in order to
specify the aufs backingstore.

This first check is the one were we only want to specify --snapshot
when we have btrfs or aufs, but not in the case where we want to clone
without aufs.

https://codereview.appspot.com/74660044/diff/1/provider/local/config.go
File provider/local/config.go (right):

https://codereview.appspot.com/74660044/diff/1/provider/local/config.go#newco...
provider/local/config.go:29: "lxc-clone-aufs": schema.String(),
On 2014/03/17 03:08:52, wallyworld wrote:
> why not schema.Bool()?
> (used with schema.Defaults to ensure default is true)

Because there wasn't an easy way to identify whether
it was set or not.  I needed three states, yes, no and
missing.  If it is missing, and the container is lxc then
we specify values. If they are specified, we use them.

[thumper, 2014-03-17 04:28:13]

Please take a look.

[wallyworld, 2014-03-17 04:35:12]

LGTM with typo fix

https://codereview.appspot.com/74660044/diff/10011/cmd/juju/help_topics.go
File cmd/juju/help_topics.go (right):

https://codereview.appspot.com/74660044/diff/10011/cmd/juju/help_topics.go#ne...
cmd/juju/help_topics.go:90: in the configuration for you local provider.  If you
have the main  container
s/you/your