Refactoring CreateTestRepository

Now each git command is a function
(continued)
```go
func CreateFile(testPath, file, content string) error {
	now := time.Now().UnixNano()
	if file == "" {
		file = fmt.Sprintf("README_%d", now)
	}
	if content == "" {
		content = fmt.Sprintf("much WOW %d", now)
	}
	return ioutil.WriteFile(path.Join(testPath, file), []byte(content), 0644)
}
```