Use program version from git tag

This should fix issue #51.

Author: mvp

Makefile

@@ -14,6 +14,8 @@ RM		:= rm -rf
 CC ?= gcc
 CFLAGS ?= -g -O0
 CFLAGS += -Wall -Wextra -std=c99 -pedantic
+GIT_VERSION := $(shell git describe --abbrev=4 --dirty --always --tags)
+CFLAGS += -DPROGRAM_VERSION=\"$(GIT_VERSION)\"
 
 ifeq ($(UNAME_S),Linux)
 	LDFLAGS += -Wl,-z,relro -lusb-1.0

uhubctl.c

@@ -9,7 +9,6 @@
  *
  */
 
-#define PROGRAM_VERSION "1.8"
 #define _XOPEN_SOURCE 500
 
 #include <stdio.h>
@@ -181,7 +180,7 @@ static const struct option long_options[] = {
 int print_usage()
 {
     printf(
-        "uhubctl v%s: utility to control USB port power for smart hubs.\n"
+        "uhubctl %s: utility to control USB port power for smart hubs.\n"
         "Usage: uhubctl [options]\n"
         "Without options, show status for all smart hubs.\n"
         "\n"