How to Run Grunt Email Builder to Process Only Specific Folder

Question

I'm using grunt email builder combined with Pug and Watch to create my emails.

But I want to make it automatically process only the specific folder (current working folder directory) when I run grunt by default, because Grunt Email Builder is processing all files in the folder and subfolder that makes it heavier by the time.

grunt email builder process all the folder and takes time to process when I change only one content

Is there possible to do it? If yes how to do it properly?

Thanks!