Directly serve 404 if no favicon.ico file exists

Closes #6

http.go

@@ -202,6 +202,11 @@ func (a *goBlog) buildRouter() (http.Handler, error) {
 	// Robots.txt
 	r.With(cacheLoggedIn, a.cacheMiddleware).Get(robotsTXTPath, a.serveRobotsTXT)
 
+	// Favicon
+	if !hasStaticPath("favicon.ico") {
+		r.With(cacheLoggedIn, a.cacheMiddleware).Get("/favicon.ico", a.serve404)
+	}
+
 	r.NotFound(a.servePostsAliasesRedirects())
 
 	r.MethodNotAllowed(a.serveNotAllowed)

staticFiles.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"os"
@@ -27,6 +28,15 @@ func allStaticPaths() (paths []string) {
 	return
 }
 
+func hasStaticPath(path string) bool {
+	// Check if file exists
+	_, err := os.Stat(filepath.Join(staticFolder, path))
+	if err != nil && errors.Is(err, os.ErrNotExist) {
+		return false
+	}
+	return true
+}
+
 // Gets only called by registered paths
 func (a *goBlog) serveStaticFile(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Cache-Control", fmt.Sprintf("public,max-age=%d,s-max-age=%d,stale-while-revalidate=%d", a.cfg.Cache.Expiration, a.cfg.Cache.Expiration/3, a.cfg.Cache.Expiration))