Add version in usage, improve usage

Dockerfile

@@ -1,6 +1,8 @@
 FROM ubuntu
 
 RUN apt-get update && apt-get install --no-install-recommends -y build-essential gdb && rm -rf /var/lib/apt/lists/*
+RUN apt-get update
+RUN apt-get install --no-install-recommends -y git
 
 ADD . /tini
 RUN cd /tini && make clean && make

config.mk

@@ -1,10 +1,11 @@
-VERSION = 0.1.0
+VERSION=0.2.0
+GIT_REV=$(shell git log -n 1 --date=local --pretty=format:"%h")
 
 # paths
 PREFIX=/usr/local
 
 CC = cc
 LD = $(CC)
-CPPFLAGS=-D_FORTIFY_SOURCE=2
+CPPFLAGS=-D_FORTIFY_SOURCE=2 -DTINI_VERSION="\"$(VERSION) - $(GIT_REV)\""
 CFLAGS=-std=gnu99 -Wextra -Wall -pedantic -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security
 LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro -Wl,-s

ddist.sh

@@ -13,6 +13,6 @@ NAME="${IMG}-dist"
 BIN="tini"
 
 docker build -t "${IMG}" .
-docker run -it --name="${NAME}" --entrypoint="true" "${IMG}" true
+docker run -it --name="${NAME}" "${IMG}" true "-h"
 docker cp "${NAME}:/tini/${BIN}" "${DIST_DIR}"
 docker rm "${NAME}"

tini.c

@@ -1,4 +1,6 @@
 /* See LICENSE file for copyright and license details. */
+#define _GNU_SOURCE
+
 #include <sys/types.h>
 #include <sys/wait.h>
 
@@ -11,6 +13,9 @@
 #include <unistd.h>
 #include <stdbool.h>
 
+#ifndef TINI_VERSION
+#define TINI_VERSION "???"
+#endif
 
 #define PRINT_FATAL(...)    fprintf(stderr, "[FATAL] "); fprintf(stderr, __VA_ARGS__); fprintf(stderr, "\n");
 #define PRINT_WARNING(...)  if (verbosity > 0) { fprintf(stderr, "[WARN ] "); fprintf(stderr, __VA_ARGS__); fprintf(stderr, "\n"); }
@@ -51,7 +56,12 @@ int spawn(const sigset_t* const child_sigset_ptr, char (*argv[]), int* const chi
 
 
 void print_usage(char* const name, FILE* const file) {
-	fprintf(file, "Usage: %s [-h | program arg1 arg2]\n", name);
+	fprintf(file, "%s (version %s)\n", basename(name), TINI_VERSION);
+	fprintf(file, "Usage: %s [OPTIONS] PROGRAM -- [ARGS]\n\n", basename(name));
+	fprintf(file, "Execute a program under the supervision of a valid init process (%s)\n\n", basename(name));
+	fprintf(file, "  -h: Show this help message and exit.\n");
+	fprintf(file, "  -v: Generate more verbose output. Repeat up to 4 times.\n");
+	fprintf(file, "\n");
 }