The issue here is that when a middleware failed and a recovery sequence
started, it would halt at the "call" step because the "Call" didn't
properly recover the child sequence.
An additional issue was that a Warden had no "recover" method, meaning
embedded Wardens wouldn't recover their stacks properly.
This works by registering a `config` with `:provider => true` with the
same name as your provider. Vagrant will then automatically configure
the provider when `config.vm.provider` is used.
Boxes are provider-specific, and we don't know the provider until
Environment#machine is called, so we need to build up the machine
configuration during this time.
This will eventually replace the Environment#vms method. Because of the
introduction of providers, the environment doesn't know what the backing
of the machines will be (and they're _machines_ now, not _vms_).
Instead, users of Environment will now call `#machine` on the
environment to retrieve a machine with the given backing provider as it
needs it.
This is done by calling the `upgrade` method on the _old_ configuration
classes. The old configuration classes are given the complete new
configuration and can set whatever settings they need to on it.
These are classes that use NO core classes of Vagrant, and are therefore
safe to load for upgrades. i.e. a V2 core can load a V1 config class
that is deemed upgrade safe without crashing Vagrant.
Before we were manually going over every plugin and getting each piece,
all over the place. Now we have a central manager that will give us all
the pieces we want. There is still some cleanup to do here but this is
much better overall.
The built-in middleware sequences will now be hardcoded onto
Vagrant::Action. Other plugins can hook into these sequences to provide
verification and so on. So the VirtualBox plugin will hook into that
action sequence and add verification.
This works by now calling the `:ssh` action on the provider. This action
is allowed to do whatever it pleases, but should at some point probably
call the `SSHExec` built-in middleware.
The `SSHExec` built-in middleware was added. This uses the information
returned by `Machine#ssh_info` and uses the `Vagrant::Util::SSH` helper
to exec into the remote machine. The provider should do any work upfront
in verifying that the machine is ready to be SSHed into.
