  build/%: %
  	@mkdir -p $(@D)
  	@cp -r $< $@
  
  html: $(DEPS) $(OBJ)
  	make -C build html
  	cp -r img/frontpage/ build/_build/html/_images/
  
  TEX=build/_build/latex/d2l-zh.tex
  
 
</s> remove     url='https://github.com/mli/gluon-tutorials-zh',
 </s> add     url='http://www.diveintodeeplearning.org', </s> remove 	rm -rf build/chapter* build/_build $(DEPS) $(PKG)
 </s> add 	rm -rf build/chapter* build/_build build/img build/data build/environment.yml build/README.md $(PKG)
 </s> remove ORIGN_DEPS = $(IMG_NOTEBOOK) $(wildcard data/*) environment.yml README.md
DEPS = $(patsubst %, build/%, $(ORIGN_DEPS))
 </s> add IMG_NOTEBOOK = $(filter-out $(FRONTPAGE_DIR), $(wildcard img/*))
ORIGIN_DEPS = $(IMG_NOTEBOOK) $(wildcard data/*) environment.yml README.md
DEPS = $(patsubst %, build/%, $(ORIGIN_DEPS)) </s> remove FRONTPAGE = $(wildcard img/frontpage/*)
IMG_NOTEBOOK = $(filter-out $(FRONTPAGE), $(wildcard img/*))
 </s> add FRONTPAGE_DIR = img/frontpage
FRONTPAGE = $(wildcard $(FRONTPAGE_DIR)/*)
FRONTPAGE_DEP = $(patsubst %, build/%, $(FRONTPAGE))
html: $(DEPS) $(FRONTPAGE_DEP) $(OBJ)
  build/%: %
  	@mkdir -p $(@D)
  	@cp -r $< $@
  
html: $(DEPS) $(FRONTPAGE_DEP) $(OBJ)
  	make -C build html
  	cp -r img/frontpage/ build/_build/html/_images/
  
  TEX=build/_build/latex/d2l-zh.tex
  
keep keep keep keep replace keep keep keep keep keep
 add frontpage dep, clean unused files in build/, and modify Makefile 
Makefile