SVN pre-commit hook that catches conflict markers

SvnConflictCatcher.php

#!/usr/local/bin/php
<?php
/**
 * Pre-commit Subversion script.
 * @author Omni Adams <omni@digitaldarkness.com>
 */


/**
 * Path to the awk binary.
 */
define('AWK', '/usr/bin/awk');

/**
 * Path to the grep binary.
 */
define('GREP', '/bin/grep');

/**
 * Path to svnlook binary.
 */
define('SVNLOOK', '/usr/bin/svnlook');

/**
 * Divider to inject into error messages.
 */
define('DIVIDER',
    '********************************************************************************');


/**
 * Scan changed files for SVN conflict markers.
 *
 * If any of he changed files contain >>>>>>, =======, or
 * <<<<<<, writes an error message to standard error and
 * returns true.
 * @param string $transaction SVN transaction ID.
 * @param string $repository Full path to the repository.
 * @return boolean True if there was an error.
 */
function catchSvnArtifacts($transaction, $repository) {
    $errors = false;
    $changedCommand = SVNLOOK . ' changed -t "'
        . $transaction . '" "'
        . $repository . '" '
        . '| ' . GREP . ' "^[UA]" '
        . '| ' . AWK . ' \'{print $2}\'';

    $changedOutput = array();
    exec($changedCommand, $changedOutput);
    foreach ($changedOutput as $file) {
        $conflicts = '';
        $conflictCommand = SVNLOOK . ' cat -t "'
            . $transaction . '" "'
            . $repository . '" "' . $file . '" '
            . '| ' . GREP . ' -E '
            . '"(<<<<<<)|(=======)|(>>>>>>)"';
        exec($conflictCommand, $conflicts);
        if (array() == $conflicts) {
            continue;
        }
        $message = PHP_EOL . DIVIDER . PHP_EOL . PHP_EOL
            . $file . ' contains unresolved Subversion '
            . 'conflict markers.' . PHP_EOL;
        file_put_contents('php://stderr', $message);
        $errors = true;
    }
    return $errors;
}

$repository = $_SERVER['argv'][1];
$transaction = $_SERVER['argv'][2];
if (catchSvnArtifacts($transaction, $repository)) {
    exit(1);
}

exit(0);