pre-build.pl

#!/usr/bin/env perl

use strict;

system('mkdir -p build/');

my $versionHeader = 'build/app_git_version.h';

my $gitVer;

$gitVer = `git describe --tags 2>/dev/null`;
chomp $gitVer;

if ($?) {
    `git log -1 2>&1 >/dev/null`;
    if ($?) {
        $gitVer = 'no-git-commits';
    } else {
        my $commitNum = `git rev-list --count HEAD`;
        chomp $commitNum;
        my $commitHash = `git rev-parse HEAD`;
        $commitHash = substr($commitHash, 0, 7);
        $gitVer = "v$commitNum-$commitHash";
    }
}

{
    open(my $fh, '>', "$versionHeader.new") || die "failed to write git version: $!";
    print $fh <<"END";
#pragma once

#define APP_GIT_VERSION "$gitVer"
END
}

rename("$versionHeader.new", $versionHeader) if !-e $versionHeader || `diff $versionHeader $versionHeader.new`;
unlink("$versionHeader.new");