Simple PHP script to find out wich commit broke given test command.

find_who_breaks.php

<?php

$sinceDate = '11/01/2012'; // Change to fit your needs
$testCommand = 'phpunit src/Symfony/Component/Finder'; // Change to fit your needs

$revlist = array();

exec("git log --since=$sinceDate --branches=master --reverse --pretty=%H | cat", $revlist);

foreach ($revlist as $commit) {
    echo "Checking out commit $commit...\r\n";
    system("git checkout $commit");
    echo "Running tests...\r\n";
    $return = null;
    system($testCommand, $return);

    if ($return !== 0) {
        break;
    }
}

echo "Blame on $commit !!!\r\n";