add function upgrade or uninstall a specific version

Makefile

@@ -11,7 +11,7 @@ PKG=$(PKG_DIR)/$(PKG_NAME).tar.gz
 #SIG=$(PKG_DIR)/$(PKG_NAME).asc
 
 PREFIX?=/usr/local
-DOC_DIR=$(PREFIX)/share/doc/$(PKG_NAME)
+DOC_DIR=$(PREFIX)/share/doc/$(NAME)
 
 pkg:
 	@mkdir -p $(PKG_DIR)
@@ -47,13 +47,18 @@ install:
 	@echo "Install all files into $(PREFIX)/"
 	@for dir in $(INSTALL_DIRS); do sudo mkdir -p $(PREFIX)/$$dir; done
 	@for file in $(INSTALL_FILES); do sudo cp $$file $(PREFIX)/$$file; done
-	@sudo mkdir -p $(DOC_DIR)
-	@sudo cp -r README.md $(DOC_DIR)/
+	@sudo mkdir -p $(DOC_DIR)-$(VERSION)
+	@sudo cp -r README.md $(DOC_DIR)-$(VERSION)/
 	@echo -e "\nCongrats! Now you should be able to run '$(PKG_NAME)' from your PATH\n"
 
+upgrade:
+	@echo "Upgrade $(NAME) from $(version) to $(VERSION)"
+	@$(uninstall) version=$(version)
+	@$(install)
+
 uninstall:
-	@echo "Uninstall all files from $(PKG_NAME)"
+	@echo "Uninstall all files from $(NAME)-$(version)"
 	@for file in $(INSTALL_FILES); do sudo rm -f $(PREFIX)/$$file; done
-	@sudo rm -r $(DOC_DIR)
+	@sudo rm -r $(DOC_DIR)-$(version)
 
 .PHONY: build clean test tag release install uninstall all