function cp() {
        logger.info(
            'installing',
            name + '@' + v + (from_cache ? ' (cached)': '')
        );
        utils.ensureDir(opt.target_dir, function (err) {
            if (err) {
                return callback(err);
            }
            utils.cp('-r', cdir, p, function (err) {
                return callback(err);
            });
        });
    }
Copies a directory into the local target directory. Writes log messages
during this process.

@param {String} name - the name of the package being copied
@param {String} v - the version of the package
@param {Boolean} from_cache - whether we're installing a cached package
@param {Object} opt - the options object
@param {Function} callback