Jade template as a preprocessor for html

I will not be using node.js in production, but I like jades syntax, so I would like to compile jade template into html when developing.

Given this file structure:

app/
  jade_templates /
    index.jade
    subfolder /
      subpage.jade
  html_templates /
    index.html
    subfolder /
      subpage.html

I would like to have a script that watches the jade_templates directory and compiles the corresponding html template to html_templates any time a change has been made.

How can this be accomplished?

Thank you.

EDIT The Jade README has this Sample Makefile, but I'm not sure how to adapt this to my needs.

JADE = $(shell find pages/*.jade)
HTML = $(JADE:.jade=.html)

all: $(HTML)

%.html: %.jade
    jade < $< --path $< > $@

clean:
    rm -f $(HTML)

.PHONY: clean