build: get rid of "new" target

Makefile

@@ -1,7 +1,7 @@
 GO = go
 BIN = bin/aoc
 
-.PHONY: build test clean new
+.PHONY: build test clean
 
 build:
 	@mkdir -p $(dir $(BIN))
@@ -13,53 +13,51 @@ test:
 clean:
 	@rm -f $(BIN)
 
-new:
-	@if [ -z "$(filter-out $@,$(MAKECMDGOALS))" ]; then \
-		echo "Usage: make new 2020D9"; \
-		exit 1; \
-	fi
-	@DAY_ARG=$$(echo $(filter-out $@,$(MAKECMDGOALS)) | awk '{print $$1}'); \
-	YEAR=$$(echo $$DAY_ARG | sed 's/D.*//'); \
-	DAY_NUM=$$(echo $$DAY_ARG | sed 's/.*D//'); \
-	DAY_NAME=$$(case $$DAY_NUM in \
-		1) echo "One" ;; \
-		2) echo "Two" ;; \
-		3) echo "Three" ;; \
-		4) echo "Four" ;; \
-		5) echo "Five" ;; \
-		6) echo "Six" ;; \
-		7) echo "Seven" ;; \
-		8) echo "Eight" ;; \
-		9) echo "Nine" ;; \
-		10) echo "Ten" ;; \
-		11) echo "Eleven" ;; \
-		12) echo "Twelve" ;; \
-		13) echo "Thirteen" ;; \
-		14) echo "Fourteen" ;; \
-		15) echo "Fifteen" ;; \
-		16) echo "Sixteen" ;; \
-		17) echo "Seventeen" ;; \
-		18) echo "Eighteen" ;; \
-		19) echo "Nineteen" ;; \
-		20) echo "Twenty" ;; \
-		21) echo "TwentyOne" ;; \
-		22) echo "TwentyTwo" ;; \
-		23) echo "TwentyThree" ;; \
-		24) echo "TwentyFour" ;; \
-		25) echo "TwentyFive" ;; \
-		*) echo "Unknown" ;; \
-	esac); \
-	mkdir -p internal/$$YEAR/Day$$DAY_NAME; \
-	mkdir -p internal/data/$$YEAR/Day$$DAY_NAME; \
-	touch internal/$$YEAR/Day$$DAY_NAME/code.go; \
-	touch internal/$$YEAR/Day$$DAY_NAME/code_test.go; \
-	if [ -n "$$ADVENTOFCODE_SESSION" ]; then \
-		curl -s -H "Cookie: session=$$ADVENTOFCODE_SESSION" \
-			https://adventofcode.com/$$YEAR/day/$$DAY_NUM/input \
-			| perl -pe 'chomp if eof' > internal/data/$$YEAR/Day$$DAY_NAME/input.txt; \
-	else \
-		touch internal/data/$$YEAR/Day$$DAY_NAME/input.txt; \
-	fi; \
-
 %:
-	@:
+	@DAY_ARG=$@; \
+	if echo $$DAY_ARG | grep -qE '^[0-9]{4}D[0-9]+$$'; then \
+		YEAR=$$(echo $$DAY_ARG | sed 's/D.*//'); \
+		DAY_NUM=$$(echo $$DAY_ARG | sed 's/.*D//'); \
+		DAY_NAME=$$(case $$DAY_NUM in \
+			1) echo "One" ;; \
+			2) echo "Two" ;; \
+			3) echo "Three" ;; \
+			4) echo "Four" ;; \
+			5) echo "Five" ;; \
+			6) echo "Six" ;; \
+			7) echo "Seven" ;; \
+			8) echo "Eight" ;; \
+			9) echo "Nine" ;; \
+			10) echo "Ten" ;; \
+			11) echo "Eleven" ;; \
+			12) echo "Twelve" ;; \
+			13) echo "Thirteen" ;; \
+			14) echo "Fourteen" ;; \
+			15) echo "Fifteen" ;; \
+			16) echo "Sixteen" ;; \
+			17) echo "Seventeen" ;; \
+			18) echo "Eighteen" ;; \
+			19) echo "Nineteen" ;; \
+			20) echo "Twenty" ;; \
+			21) echo "TwentyOne" ;; \
+			22) echo "TwentyTwo" ;; \
+			23) echo "TwentyThree" ;; \
+			24) echo "TwentyFour" ;; \
+			25) echo "TwentyFive" ;; \
+			*) echo "Unknown" ;; \
+		esac); \
+		mkdir -p internal/$$YEAR/Day$$DAY_NAME; \
+		mkdir -p internal/data/$$YEAR/Day$$DAY_NAME; \
+		touch internal/$$YEAR/Day$$DAY_NAME/code.go; \
+		touch internal/$$YEAR/Day$$DAY_NAME/code_test.go; \
+		if [ -n "$$ADVENTOFCODE_SESSION" ]; then \
+			curl -s -H "Cookie: session=$$ADVENTOFCODE_SESSION" \
+				https://adventofcode.com/$$YEAR/day/$$DAY_NUM/input \
+				| perl -pe 'chomp if eof' > internal/data/$$YEAR/Day$$DAY_NAME/input.txt; \
+		else \
+			touch internal/data/$$YEAR/Day$$DAY_NAME/input.txt; \
+		fi; \
+		echo "$$DAY_ARG ready to be solved."; \
+	else \
+		:; \
+	fi