add manpage

Makefile

@@ -1,8 +1,9 @@
-CC	   ?= gcc
-CFLAGS += -Wall -Wextra
-LIBS	= -lcurses
+ASCIIDOC ?= a2x
+CC       ?= gcc
+CFLAGS   := -Wall -Wextra $(CFLAGS)
+LIBS      = -lcurses
 
-all: 2048
+.PHONY: clean man man-nc
 
 2048: src/2048.c
 	$(CC) $(CFLAGS) $(LDFLAGS) $(LIBS) src/2048.c -o 2048
@@ -10,5 +11,15 @@ all: 2048
 2048nc: src/2048.c
 	$(CC) -DNO_CURSES=1 $(CFLAGS) $(LDFLAGS) src/2048.c -o 2048nc
 
+all: 2048
+
 clean:
 	rm -f 2048 2048nc
+
+man:
+	rm -f man/2048.1
+	$(ASCIIDOC) -d manpage -f manpage man/2048.1.txt
+
+man-nc:
+	rm -f man/2048nc.1
+	$(ASCIIDOC) -d manpage -f manpage man/2048nc.1.txt