src/Composer/Command/InitCommand.php
protected function hasVendorIgnore($ignoreFile, $vendor = 'vendor')
    {
        if (!file_exists($ignoreFile)) {
            return false;
        }

        $pattern = sprintf('{^/?%s(/\*?)?$}', preg_quote($vendor));

        $lines = file($ignoreFile, FILE_IGNORE_NEW_LINES);
        foreach ($lines as $line) {
            if (preg_match($pattern, $line)) {
                return true;
            }
        }

        return false;
    }
protected function hasVendorIgnore($ignoreFile, $vendor = 'vendor')
    {
        if (!file_exists($ignoreFile)) {
            return false;
        }

        $pattern = sprintf('{^/?%s(/\*?)?$}', preg_quote($vendor));

        $lines = file($ignoreFile, FILE_IGNORE_NEW_LINES);
        foreach ($lines as $line) {
            if (preg_match($pattern, $line)) {
                return true;
            }
        }

        return false;
    }
Checks the local .gitignore file for the Composer vendor directory.

Tested patterns include:
"/$vendor"
"$vendor"
"$vendor/"
"/$vendor/"
"/$vendor/*"
"$vendor/*"

@param string $ignoreFile
@param string $vendor

@return bool