In drush/commands/pm/package_handler/wget,inc
// Add to URL so it is part of the cache key . Dev snapshots can then be cached forever.
if (strpos($release['download_link'], '-dev') !== FALSE) {
$release['download_link'] .= '?date=' . $release['date'];
}
$filename = basename($release['download_link']);should probably be replaced with this:
$filename = basename($release['download_link']);
// Add to URL so it is part of the cache key . Dev snapshots can then be cached forever.
if (strpos($release['download_link'], '-dev') !== FALSE) {
$release['download_link'] .= '?date=' . $release['date'];
}Reference: https://drupal.org/node/1801788