Fix rendering all markdown by default. (#190)

* Fix rendering all markdown by default.

* Fix formatting.

* Apply Copilot recommendations.

Author: patrickdappollonio

internal/server/handlers.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"slices"
 	"sort"
 	"strings"
 	"unicode/utf8"
@@ -83,7 +84,21 @@ func (s *Server) showOrRender(w http.ResponseWriter, r *http.Request) {
 	// If the path is not a directory, then it's a file, so we can render it,
 	// let's check first if it's a markdown file
 	if ext := strings.ToLower(filepath.Ext(currentPath)); ext == ".md" || ext == ".markdown" {
-		s.serveMarkdown(currentPath, w, r)
+		// Check FullMarkdownRender first to avoid unnecessary filename extraction
+		if s.FullMarkdownRender {
+			s.serveMarkdown(currentPath, w, r)
+			return
+		}
+
+		// Not rendering all markdown, check if this is an index-like file
+		filename := filepath.Base(currentPath)
+		if slices.Contains(allowedIndexFiles, filename) {
+			s.serveMarkdown(currentPath, w, r)
+			return
+		}
+
+		// If not an index file and FullMarkdownRender is disabled, serve as plain text
+		s.serveFile(0, currentPath, w, r)
 		return
 	}