Merge pull request #34 from spowelljr/fixPowershellDetection

Fix Powershell in CMD being mis-detected

libmachine/shell/shell_windows.go

@@ -52,7 +52,9 @@ func getNameAndItsPpid(pid int) (exefile string, parentid int, err error) {
 func Detect() (string, error) {
 	shell := os.Getenv("SHELL")
 
-	if shell == "" {
+	// if you spawn a Powershell instance from CMD, sometimes the SHELL environment variable still points to CMD in the Powershell instance
+	// so if SHELL is pointing to CMD, let's do extra work to get the correct shell
+	if shell == "" || filepath.Base(shell) == "cmd" {
 		shell, shellppid, err := getNameAndItsPpid(os.Getppid())
 		if err != nil {
 			return "cmd", err // defaulting to cmd