add flag to print version and exit

Makefile

@@ -1,6 +1,6 @@
 include config.mk
 
-CFLAGS += -I. -DWLR_USE_UNSTABLE -std=c99 -pedantic
+CFLAGS += -I. -DWLR_USE_UNSTABLE -std=c99 -pedantic -DVERSION=\"$(VERSION)\"
 
 WAYLAND_PROTOCOLS=$(shell pkg-config --variable=pkgdatadir wayland-protocols)
 WAYLAND_SCANNER=$(shell pkg-config --variable=wayland_scanner wayland-scanner)

config.mk

@@ -1,3 +1,6 @@
+_VERSION = 0.3.1
+VERSION = $(shell ./generate-version.sh $(_VERSION))
+
 # paths
 PREFIX = /usr/local
 MANDIR = $(PREFIX)/share/man

dwl.c

@@ -2516,9 +2516,11 @@ main(int argc, char *argv[])
 	char *startup_cmd = NULL;
 	int c;
 
-	while ((c = getopt(argc, argv, "s:h")) != -1) {
+	while ((c = getopt(argc, argv, "s:hv")) != -1) {
 		if (c == 's')
 			startup_cmd = optarg;
+		else if (c == 'v')
+			die("dwl " VERSION);
 		else
 			goto usage;
 	}

generate-version.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+if git tag --contains HEAD | grep -q $1; then
+	echo $1
+else
+	branch="$(git rev-parse --abbrev-ref HEAD)"
+	commit="$(git rev-parse --short HEAD)"
+	if [ "${branch}" != "main" ]; then
+		echo $1-$branch-$commit
+	else
+		echo $1-$commit
+	fi
+fi