dir: Avoid looping through all the feeds

Maintain a map of feeds to avoid looping through all the configured
feeds for a task.

dir.go

@@ -153,14 +153,8 @@ func (d *Dir) _read(srcDir, path string, task *Task, cfg *Site) error {
 
 // process processes the directory's contents.
 func (d *Dir) process(cfg *Site, task *Task) error {
-	// build feeds
-	// this must happen before the page processing
-	// to have an unprocessed Page.Content
-	// 192: d.Pages[i].Content = b.String()
-	for _, feed := range task.Feeds {
-		if d.path != feed.InputDir {
-			continue
-		}
+	// Build feeds before templates are applied to the page contents
+	for _, feed := range task.feeds[d.path] {
 		b, err := d.buildFeed(cfg, feed)
 		if err != nil {
 			return err

site.go

@@ -35,6 +35,7 @@ type Task struct {
 	OutputDir   string            `toml:"output_dir"`  // output directory
 	UglyURLs    bool              `toml:"ugly_urls"`   // whether to use ugly URLs
 	Feeds       []Feed            `toml:"feeds"`
+	feeds       map[string][]Feed
 }
 
 type Feed struct {
@@ -91,6 +92,14 @@ func LoadSite(config string) (*Site, error) {
 		return nil, err
 	}
 
+	// Populate task feeds map
+	for _, task := range site.Tasks {
+		task.feeds = map[string][]Feed{}
+		for _, feed := range task.Feeds {
+			task.feeds[feed.InputDir] = append(task.feeds[feed.InputDir], feed)
+		}
+	}
+
 	// deprecate [feeds]
 	if len(site.Feeds) > 0 {
 		log.Println("The [feeds] configuration is deprecated")