Fix interactive shell when using native-client

[gbraad]

This fixes the way the ssh command is invoking the shell, and will therefore allow interactive use with the Go native client.

Steps to reproduce:

$ sudo mv /usr/bin/ssh /usr/bin/-ssh
$ minikube start
$ minikube ssh
$ 

Expected:

$ sudo mv /usr/bin/ssh /usr/bin/-ssh
$ minikube start
$ minikube ssh 
                        ##         .
                  ## ## ##        ==
               ## ## ## ## ##    ===
           /"""""""""""""""""\___/ ===
      ~~~ {~~ ~~~~ ~~~ ~~~~ ~~~ ~ /  ===- ~~~
           \______ o           __/
             \    \         __/
              \____\_______/
 docker@minikube:~$

Due to #1531 I am unable to verify the build myself...

We invoke the shell as follows https://github.com/kubernetes/minikube/blob/master/pkg/minikube/cluster/cluster.go#L537

	return client.Shell(strings.Join(args, " "))

What happens is that we provide an empty string instead of no value: https://play.golang.org/p/z7DDUWnuYm You can verify this with:

package main

import (
	"strings"
	"fmt"
	
)

func main() {
	args := []string {}
	command := strings.Join(args, " ")
	fmt.Printf("Type: %T, Length: %v, Value: %v.\n", command, len(command), command)
}

At https://github.com/docker/machine/blob/master/libmachine/ssh/client.go#L269 the use of args ...string will result in args having a length of 1.

func (client *NativeClient) Shell(args ...string) error {

this means that the check at https://github.com/docker/machine/blob/master/libmachine/ssh/client.go#L318 wrongly assumes that arguments are given, and it will execute https://github.com/docker/machine/blob/master/libmachine/ssh/client.go#L324

		session.Run(strings.Join(args, " "))

Docker machine itself uses a different way to invoke the shell https://github.com/docker/machine/blob/e1a03348ad83d8e8adb19d696bc7bcfb18ccd770/commands/ssh.go#L50

	return client.Shell(c.Args().Tail()...)

Therefore fixing this with:

	return client.Shell(args...)

[minikube-bot]

Can one of the admins verify this patch?

[codecov-io]

Codecov Report

Merging #1571 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1571   +/-   ##
=======================================
  Coverage   39.52%   39.52%           
=======================================
  Files          50       50           
  Lines        2548     2548           
=======================================
  Hits         1007     1007           
  Misses       1375     1375           
  Partials      166      166

Impacted Files	Coverage Δ
pkg/minikube/cluster/cluster.go	45.96% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 94cb85f...03d3e1f. Read the comment docs.

[dlorenc]

@minikube-bot ok to test

[r2d4]

Nice, thanks!

[gbraad]

@r2d4

Linux-KVM-Alt fails with:

+ pushd /home/jenkins/go/src/github.com/r2d4/docker-machine-driver-kvm
linux_integration_tests_kvm_alt.sh: line 36: pushd: /home/jenkins/go/src/github.com/r2d4/docker-machine-driver-kvm: No such file or directory
Build step 'Execute shell' marked build as failure

and no visible output for the Windows-HyperV test.

[r2d4]

Yeah thats fine - those are just problems with the testing infrastructure. I'll resolve the Linux-Alt driver issue separately later.