including git-hash in a C program.

githash.h

#ifndef GIT_HASH
#define GIT_HASH "f2607d7e246549d9ea54922a87001459c0235486"
#endif

Makefile

a.out: test.c githash.h
	gcc $<
githash.h:
	echo  -n '#ifndef GIT_HASH\n#define GIT_HASH "' > $@ && \
	git rev-parse HEAD | tr -d "\n" >> $@ && \
	echo  '"\n#endif' >> $@

post-commit

#!/bin/sh
rm -f githash.h

test.c

#include <stdio.h>
#include "githash.h"

int main(int argc,char** argv)
	{
	return fputs("Git-Version:" GIT_HASH "\n",stdout)==0;
	}