Returns the base of the URL to fetch available update data for a project.
$project: The array of project information from update_get_projects().
The base of the URL used for fetching available update data. This does not include the path elements to specify a particular project, version, site_key, etc.
function _update_get_fetch_url_base($project) {
return isset($project['info']['project status url']) ? $project['info']['project status url'] : variable_get('update_fetch_url', UPDATE_DEFAULT_URL);
}