make tags target for ctags

I want to generate ctags whenever I make

.gitignore

@@ -0,0 +1 @@
+tags

makefile

@@ -7,7 +7,7 @@ TESTBIN := /tmp/all_tests
 
 .PHONY: test
 
-test:
+test: tags
 	@echo "Discovering test files..."
 	@files=$$(find . -type f -name 'test*.c'); \
 	if [ -z "$$files" ]; then \
@@ -18,3 +18,11 @@ test:
 		echo "Running tests..."; \
 		$(TESTBIN); \
 	fi
+
+
+PROJECT_ROOT := $(shell pwd)
+PROJECT_C_FILES := $(shell find $(PROJECT_ROOT) \( -name '*.c' -o -name '*.h' \))
+CRITERION_HEADERS := $(shell find /usr/include/criterion)
+ALL_FILES := $(PROJECT_C_FILES) $(CRITERION_HEADERS)
+tags: $(ALL_FILES)
+	ctags $(ALL_FILES)