Search for public git repositories in the Alexa 1 million top ranked websites list, see: https://royduineveld.nl/hacking-public-git-repositories/

crawl.php

<?php
// Download the list from: http://s3.amazonaws.com/alexa-static/top-1m.csv.zip
$csv = file_get_contents('top-1m.csv');
$lines = explode(PHP_EOL,$csv);

$counter = 1;
foreach($lines as $line){
	$url = explode(',',$line)[1];
	echo $counter.' '.$url.PHP_EOL;

	$gitUrl = 'http://'.$url.'/.git/config';
	$content = file_get_contents($gitUrl);
	if(strstr($content,'[core]') !== FALSE){
		echo '- YEAH! '.$gitUrl.PHP_EOL;
		$yeah[] = $gitUrl;
		file_put_contents('found.csv',$gitUrl.PHP_EOL,FILE_APPEND);
	}

	$counter++;
}

if(isset($yeah)){
	echo 'FOUND:'.PHP_EOL;
	foreach($yeah as $url){
		echo '- '.$url.PHP_EOL;
	}
}