Coffee script redux makefile with source maps

Makefile

# Coffee source (must be publicly available)
COFFEE_FOLDER = public/src/coffee/
JS_FOLDER = public/js/
COFFEE = $(shell find $(COFFEE_FOLDER) -type f -name '*.coffee')
JS = $(patsubst $(COFFEE_FOLDER)%.coffee, $(JS_FOLDER)%.js, $(COFFEE))
JS_MAP = $(patsubst $(COFFEE_FOLDER)%.coffee, $(JS_FOLDER)%.js.map, $(COFFEE))

.PHONY: all clean

all: $(JS) $(JS_MAP)

$(JS_FOLDER)%.js: $(COFFEE_FOLDER)%.coffee
	@mkdir -p "$(@D)"
	@echo Compiling "$($@)"
	coffee --js < $< > $@
	echo "//@ sourceMappingURL=$(@F).map" >> $@

$(JS_FOLDER)%.js.map: $(COFFEE_FOLDER)%.coffee
	@mkdir -p "$(@D)"
	@echo Compiling "$($@)"
	coffee --source-map -i $< | sed 's#public#..#g' > $@

clean:
	rm -rf $(JS) $(JS_MAP)