Makefile: introduced `make sync`, which creates and updates a data/ clone

Makefile

@@ -1,7 +1,7 @@
 TEMPLATES=$(wildcard root/*/*.zone.in)
 ZONES=$(addprefix stage/,$(notdir $(basename $(TEMPLATES))))
 
-.PHONY: all clean
+.PHONY: all clean sync
 
 all: $(ZONES)
 
@@ -10,6 +10,12 @@ clean:
 		ls -1 root/*/$$x.in > /dev/null 2>&1 || rm -v stage/$$x; \
 	done
 
+sync: data
+	@cd data/; git pull
+
+data:
+	git clone . data
+
 root/preprocessor.sed: root/preprocessor.sh $(wildcard root/*.in) root/servers.txt
 	@$< > $@