function getAllTasks(directories, options) {
	const allTasks = getAllAliases(options);
	for (const dir of directories) {
		const tasks = glob.sync(`${dir}/*/index.js`);
		tasks.forEach(filename => {
			const taskName = path.basename(path.dirname(filename));
			if (!allTasks[taskName]) {
				const module = require(filename);
				allTasks[taskName] = module.description || '';
			}
		});
	}
	return allTasks;
}
Return all task and alias names and descriptions from all search directories.

@param {string[]} directories
@param {Object} options
@return {Object}