Use _index for index pages

Pages with the name "index" will use the page template, and pages with
the name "_index" will use the index template.

dir.go

@@ -60,12 +60,12 @@ func (d *Dir) _read(srcDir, path string, task *Task, cfg *Config) error {
 	}
 	for _, entry := range entries {
 		name := entry.Name()
-		// Ignore names that start with "_"
+		path := pathpkg.Join(path, name)
+		if entry.IsDir() {
+			// Ignore directories beginning with "_"
 			if strings.HasPrefix(name, "_") {
 				continue
 			}
-		path := pathpkg.Join(path, name)
-		if entry.IsDir() {
 			// Gather directory data
 			dir := NewDir(path)
 			if err := dir._read(srcDir, path, task, cfg); err != nil {
@@ -73,6 +73,12 @@ func (d *Dir) _read(srcDir, path string, task *Task, cfg *Config) error {
 			}
 			d.Dirs = append(d.Dirs, dir)
 		} else if ext := pathpkg.Ext(name); task.Match(ext) {
+			// Ignore pages beginning with "_" with the exception of _index pages
+			namePrefix := strings.TrimSuffix(name, ext)
+			if strings.HasPrefix(name, "_") && namePrefix != "_index" {
+				continue
+			}
+
 			srcPath := pathpkg.Join(srcDir, path)
 			content, err := ioutil.ReadFile(srcPath)
 			if err != nil {
@@ -122,11 +128,15 @@ func (d *Dir) _read(srcDir, path string, task *Task, cfg *Config) error {
 			}
 			page.Content = string(content)
 
-			if strings.TrimSuffix(name, ext) == "index" {
+			if namePrefix == "_index" {
 				page.Path = d.Path
 				d.index = page
+			} else {
+				if namePrefix == "index" {
+					path = "/" + strings.TrimSuffix(path, name)
 				} else {
 					path = "/" + strings.TrimSuffix(path, ext)
+				}
 				if task.UglyURLs {
 					path += task.OutputExt
 				} else {