code: function filterFile(file, done) {
        if (files[file].partial) {
          // Discover whether it is explicitly declared as a partial.
          return done(null, files[file].partial)
        } else if (opts.pattern) {
          // Check if it matches the partial pattern.
          return done(null, minimatch(file, opts.pattern))
        }
        // The file is not a partial.
        done(null, false)
      }
docs: Filter out all partials