core: For dev, temporarily use branch of Childprocess, fix Win issue

Gemfile

@@ -2,6 +2,9 @@ source "http://rubygems.org"
 
 gemspec
 
+gem 'childprocess', git: "https://github.com/jarib/childprocess.git",
+  branch: "windows-inherit-stdin"
+
 if File.exist?(File.expand_path("../../vagrant-spec", __FILE__))
   gem 'vagrant-spec', path: "../vagrant-spec"
 else

lib/vagrant/action/builtin/ssh_run.rb

@@ -50,12 +50,6 @@ module Vagrant
           # don't then we default to a TTY
           if !opts[:extra_args].include?("-t") && !opts[:extra_args].include?("-T")
             opts[:extra_args] << "-t"
-
-            if Util::Platform.windows?
-              # Windows currently has a bug where STDIN won't be a TTY.
-              # This absolutely forces the allocation.
-              opts[:extra_args] << "-t"
-            end
           end
 
           opts[:extra_args] << command

lib/vagrant/util/ssh.rb

@@ -173,20 +173,8 @@ module Vagrant
         LOGGER.info("Executing SSH in subprocess: #{command_options.inspect}")
         process = ChildProcess.build("ssh", *command_options)
         process.io.inherit!
-        process.duplex = true if Platform.windows?
         process.start
-
-        if Platform.windows?
-          # On Windows, we have to mirror the STDIN to the child process.
-          while true
-            results = ::IO.select([$stdin], [], [], 0.5)
-            break if process.exited?
-            next if results[0].empty?
-            process.io.stdin.write(IO.read_until_block($stdin))
-          end
-        end
-
-        process.wait if !process.exited?
+        process.wait
         return process.exit_code
       end
     end