Makefile: replace "tgz" target with "dist"

The new target also creates a signed checksum of the archive.

Makefile

@@ -8,6 +8,8 @@ VERSION ?= $(shell cat VERSION)
 DIST_DIR = releases
 DESTDIR ?= /usr/local/bin
 TGZ_FILE ?= $(DIST_DIR)/muninlite-$(VERSION).tar.gz
+TGZ_FILE_CHECKSUM ?= $(TGZ_FILE).sha256sum
+TGZ_FILE_SIGNATURE ?= $(TGZ_FILE).asc
 
 
 $(TARGET_FILE): $(INPUT_FILE) $(PLUGIN_FILES) $(CONFIGURATION_FILE)
@@ -33,12 +35,12 @@ help:
 	@$(info   all         - assemble 'TARGET_FILE' ($(TARGET_FILE)))
 	@$(info   clean       - remove assembled 'TARGET_FILE' ($(TARGET_FILE)))
 	@$(info   clean-all   - remove old releases from 'DIST_DIR' ($(DIST_DIR)))
+	@$(info   dist        - create release archive)
 	@$(info   install     - install the standalone shell script)
 	@$(info   help        - show this overview)
 	@$(info   lint        - code style checks)
 	@$(info   spelling    - check spelling)
 	@$(info   test        - run tests)
-	@$(info   tgz         - create release archive)
 
 .PHONY: all
 all: $(TARGET_FILE)
@@ -48,8 +50,8 @@ clean-node:
 	@echo "Removing $(TARGET_FILE)"
 	@rm -f "$(TARGET_FILE)"
 
-.PHONY: clean-tgz
-clean-tgz:
+.PHONY: clean-dist
+clean-dist:
 	@echo "Removing old releases"
 	@rm -rf "$(DIST_DIR)"
 
@@ -57,10 +59,7 @@ clean-tgz:
 clean: clean-node
 
 .PHONY: clean-all
-clean-all: clean-node clean-tgz
-
-.PHONY: tgz
-tgz: $(TGZ_FILE)
+clean-all: clean-node clean-dist
 
 $(TGZ_FILE):
 	@echo "Building $@ ..."
@@ -68,6 +67,15 @@ $(TGZ_FILE):
 	git archive --prefix=muninlite-$(VERSION)/ --format=tar --output "$@.tmp" HEAD
 	mv "$@.tmp" "$@"
 
+$(TGZ_FILE_CHECKSUM): $(TGZ_FILE)
+	sha256sum "$<" >"$@"
+
+$(TGZ_FILE_SIGNATURE): $(TGZ_FILE_CHECKSUM)
+	gpg --armor --detach-sign --sign "$<"
+
+.PHONY: dist
+dist: $(TGZ_FILE_SIGNATURE)
+
 .PHONY: install
 install: $(TARGET_FILE)
 	mkdir -p "$(dir $(DESTDIR))"