def fs_write(file, contents)
      path = File.join(self.git_dir, file)
      FileUtils.mkdir_p(File.dirname(path))
      File.open(path, 'w') do |f|
        f.write(contents)
      end
    end
def fs_write(file, contents)
      path = File.join(self.git_dir, file)
      FileUtils.mkdir_p(File.dirname(path))
      File.open(path, 'w') do |f|
        f.write(contents)
      end
    end
Write a normal file to the filesystem.
   +file+ is the relative path from the Git dir
   +contents+ is the String content to be written

 Returns nothing