Generate --help output from man page

Makefile

@@ -60,7 +60,14 @@ ${BUILDDIR}/%.o: %.c
 	@mkdir -p ${@D}
 	$(CC) -c -o $@ $(CFLAGS) -MD $<
 
--include ${DEP}
+${GENDIR}/options-msg.h: ${MAN} ./gen-help.sh
+	@mkdir -p ${@D}
+	./gen-help.sh $< > $@
+
+${BUILDDIR}/args.o: CFLAGS += -I${GENDIR}
+${BUILDDIR}/args.o: ${GENDIR}/options-msg.h
 
 ${TBOBJ}:
 	$(MAKE) -C ${TBDIR} termbox.o
+
+-include ${DEP}

config.mk

@@ -26,6 +26,7 @@ BIN := ictree
 SRCDIR   := src
 INCDIR   := include
 DOCDIR   := doc
+GENDIR   := gen
 BUILDDIR := build
 
 # Termbox2 lib

gen-help.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+text="$(man -P cat -l "$1")" || exit 1
+
+echo '#define OPTIONS_MSG \'
+echo '"\\n" \'
+echo '"Options:\\n" \'
+echo "$text" |
+    sed -n -e '/^OPTIONS/,$p' |
+    sed '1d;  /^[A-Z]/q' |
+    sed '$d; s/^/"/; s/$/\\n" \\/' |
+    sed '$s/ \\$//'

gen/options-msg.h

@@ -0,0 +1,9 @@
+#define OPTIONS_MSG \
+"\n" \
+"Options:\n" \
+"       --help, -h\n" \
+"              Print a help message and exit.\n" \
+"\n" \
+"       --version, -v\n" \
+"              Display version information and exit.\n" \
+"\n"

src/args.c

@@ -21,17 +21,14 @@
 
 #include "args.h"
 #include "error.h"
+#include "options-msg.h"
 #include "version.h"
 
 #define VERSION_MSG         \
     "ictree v" VERSION "\n" \
     "Copyright 2022 Nikita Ivanov"
 
-#define HELP_MSG                               \
-    "Usage: ictree [OPTION]... [FILE]\n"       \
-    "\n"                                       \
-    "--version, -v:  print version and exit\n" \
-    "--help, -h:     print this message and exit"
+#define HELP_MSG "Usage: ictree [OPTION]... [FILE]\n" OPTIONS_MSG
 
 static struct option long_opts[] = {
     { "version", no_argument, 0, 'v' },
@@ -60,7 +57,7 @@ enum ArgAction process_args(int argc, char **argv)
             puts(VERSION_MSG);
             return ArgActionExit;
         case 'h':
-            puts(HELP_MSG);
+            printf("%s", HELP_MSG);
             return ArgActionExit;
         default:
             set_errorf("invalid option: %s", argv[opt_i + 1]);