p/l/Makefile: refactor repetitive actions

pkg.in/lists/Makefile

@@ -24,32 +24,20 @@ all: $(TARGET) $(GLOBAL_DEBUG) $(DOTBASE)
 			$(shell cp --parents -at $(TARGET) \
 				-- $(value $V))))
 
-### FIXME: move to iterator/static pattern rule
+# args: name, suffix, command
+define dump-THEM
+if [ -n "$($(1)_$(2))" ]; then echo -e "\n## $(1)_$(2)"; $(3) $($(1)_$(2)); fi;
+endef
+
+dump-PACKAGES = $(call dump-THEM,$(1),PACKAGES,echo)
+dump-LISTS = $(call dump-THEM,$(1),LISTS,cat)
+
 dot-base:
 	@# construct .base packagelist for alterator-pkg
 	@{ \
 		echo "## generated by pkg.in/lists/Makefile"; \
-		if [ -n "$(BRANDING)" ]; then \
-			echo "branding-$(BRANDING)-release"; \
-		fi; \
-		if [ -n "$(SYSTEM_PACKAGES)" ]; then \
-			echo -e "\n## SYSTEM_PACKAGES\n$(SYSTEM_PACKAGES)"; \
-		fi; \
-		if [ -n "$(COMMON_PACKAGES)" ]; then \
-			echo -e "\n## COMMON_PACKAGES\n$(COMMON_PACKAGES)"; \
-		fi; \
-		if [ -n "$(THE_PACKAGES)" ]; then \
-			echo -e "\n## THE_PACKAGES\n$(THE_PACKAGES)"; \
-		fi; \
-		if [ -n "$(BASE_PACKAGES)" ]; then \
-			echo -e "\n## BASE_PACKAGES\n$(BASE_PACKAGES)"; \
-		fi; \
-		if [ -n "$(THE_LISTS)" ]; then \
-			echo -e "\n## THE_LISTS"; cat $(THE_LISTS); \
-		fi; \
-		if [ -n "$(BASE_LISTS)" ]; then \
-			echo -e "\n## BASE_LISTS"; cat $(BASE_LISTS); \
-		fi; \
+		$(foreach p,SYSTEM COMMON THE BASE,$(call dump-PACKAGES,$(p))) \
+		$(foreach l,THE BASE,$(call dump-LISTS,$(l))) \
 	} | sed -re '/^[^[:space:]#]/ s/[[:space:]]+/\n/g' >$(TARGET)/.base
 	@if [ -n "$(THE_GROUPS)$(MAIN_GROUPS)" ]; then \
 		cp -at $(TARGET) -- $(THE_GROUPS) $(MAIN_GROUPS); \