Prior to this commit, if a user ran the `vagrant ssh -c CMD` command, it
would not allow the user to configure pseudo-terminal allocation. This
commit introduces a -t flag for the `vagrant ssh` command which defaults
to true if not specified.
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.
Brian Cain
Seth Vargo
Kalman Hazins
gnawhleinad
Mitchell Hashimoto
Paul McKellar