Add the ability to execute commands directly with the bash subcommand

In addition to provide an interactive shell, this patch adds the
'--command' and '-c' options to allow user to issue a command in the
context of a cluster.

For example:

$ k3d bash -c 'kubectl cluster-info'

cli/commands.go

@@ -355,5 +355,5 @@ func GetKubeConfig(c *cli.Context) error {
 }
 
 func Bash(c *cli.Context) error {
-	return bashShell(c.String("name"))
+	return bashShell(c.String("name"), c.String("command"))
 }

cli/shell.go

@@ -6,7 +6,7 @@ import (
 	"os/exec"
 )
 
-func bashShell(cluster string) error {
+func bashShell(cluster string, command string) error {
 	kubeConfigPath, err := getKubeConfig(cluster)
 	if err != nil {
 		return err
@@ -19,6 +19,11 @@ func bashShell(cluster string) error {
 
 	cmd := exec.Command(bashPath, "--noprofile", "--norc")
 
+	if len(command) > 0 {
+		cmd.Args = append(cmd.Args, "-c", command)
+
+	}
+
 	// Set up stdio
 	cmd.Stdout = os.Stdout
 	cmd.Stdin = os.Stdin

main.go

@@ -55,6 +55,10 @@ func main() {
 					Value: defaultK3sClusterName,
 					Usage: "Set a name for the cluster",
 				},
+				cli.StringFlag{
+					Name:  "command, c",
+					Usage: "Run a shell command in the context of the cluster",
+				},
 			},
 			Action: run.Bash,
 		},