Automatically include git version in software.

Makefile

ifeq (${VERBOSE},)
MAKEFLAGS += -s
endif

ifeq ($(OS),Windows_NT)
	PY = py
else
	PY =
endif

# Will be './' or '../'.
ROOT_DIR := $(dir $(lastword $(MAKEFILE_LIST)))

# This makes sure version.h is generated before any source file has the chance
# to include it, but does not make the objects depend on it.
${OBJECTS} ${OBJS}: | pre-build-script

.PHONY: pre-build-script
pre-build-script:
	$(PY) $(ROOT_DIR)pre-build.py

$(wildcard $(ROOT_DIR)/src/generated/*): pre-build-script
	@

.PHONY: clean-generated
clean-generated:
	$(PY) $(ROOT_DIR)pre-build.py clean

clean: clean-generated

pre-build.py

#!/usr/bin/env python3

import os
import shutil
import subprocess
import sys

os.chdir(os.path.dirname(os.path.abspath(__file__)))

git_desc = subprocess.check_output(
	['git', 'describe', '--always', '--dirty=-modified']
).decode().strip()

version_h = '// This file is automatically generated.\n'
version_h += '#pragma once\n'
version_h += '#define VERSION "{}"\n'.format(git_desc)

def write_if_changed(file_name, content):
	if os.path.exists(file_name):
		with open(file_name, 'r') as f:
			c = f.read()
		if c == content:
			return
	with open(file_name, 'w') as f:
		f.write(content)
	print('UPDATE ' + file_name)

os.makedirs('src/generated', exist_ok=True)
write_if_changed('src/generated/version.h', version_h)