change all tests to call functions instead of binary directly

I had to temporarely hack github.com/mvdan/sh to fix dir handling

init.go

@@ -4,6 +4,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"path/filepath"
 )
 
 const defaultTaskfile = `# github.com/go-task/task
@@ -14,14 +15,16 @@ default:
 `
 
 // InitTaskfile Taskfile creates a new Taskfile
-func InitTaskfile() error {
+func InitTaskfile(path string) error {
 	for _, f := range []string{"Taskfile.yml", "Taskfile.toml", "Taskfile.json"} {
+		f = filepath.Join(path, f)
 		if _, err := os.Stat(f); err == nil {
 			return ErrTaskfileAlreadyExists
 		}
 	}
 
-	if err := ioutil.WriteFile("Taskfile.yml", []byte(defaultTaskfile), 0666); err != nil {
+	f := filepath.Join(path, "Taskfile.yml")
+	if err := ioutil.WriteFile(f, []byte(defaultTaskfile), 0666); err != nil {
 		return err
 	}
 	log.Printf("Taskfile.yml created in the current directory")