Share HTML template renderers and create a watcher framework (#20218)

The recovery, API, Web and package frameworks all create their own HTML
Renderers. This increases the memory requirements of Gitea
unnecessarily with duplicate templates being kept in memory.

Further the reloading framework in dev mode for these involves locking
and recompiling all of the templates on each load. This will potentially
hide concurrency issues and it is inefficient.

This PR stores the templates renderer in the context and stores this
context in the NormalRoutes, it then creates a fsnotify.Watcher
framework to watch files.

The watching framework is then extended to the mailer templates which
were previously not being reloaded in dev.

Then the locales are simplified to a similar structure.

Fix #20210 
Fix #20211
Fix #20217

Signed-off-by: Andrew Thornton <art27@cantab.net>

modules/templates/base.go

@@ -5,15 +5,16 @@
 package templates
 
 import (
+	"fmt"
+	"io/fs"
 	"os"
+	"path/filepath"
 	"strings"
 	"time"
 
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/util"
-
-	"github.com/unrolled/render"
 )
 
 // Vars represents variables to be render in golang templates
@@ -47,8 +48,16 @@ func BaseVars() Vars {
 	}
 }
 
-func getDirAssetNames(dir string) []string {
+func getDirTemplateAssetNames(dir string) []string {
+	return getDirAssetNames(dir, false)
+}
+
+func getDirAssetNames(dir string, mailer bool) []string {
 	var tmpls []string
+
+	if mailer {
+		dir += filepath.Join(dir, "mail")
+	}
 	f, err := os.Stat(dir)
 	if err != nil {
 		if os.IsNotExist(err) {
@@ -67,8 +76,13 @@ func getDirAssetNames(dir string) []string {
 		log.Warn("Failed to read %s templates dir. %v", dir, err)
 		return tmpls
 	}
+
+	prefix := "templates/"
+	if mailer {
+		prefix += "mail/"
+	}
 	for _, filePath := range files {
-		if strings.HasPrefix(filePath, "mail/") {
+		if !mailer && strings.HasPrefix(filePath, "mail/") {
 			continue
 		}
 
@@ -76,20 +90,39 @@ func getDirAssetNames(dir string) []string {
 			continue
 		}
 
-		tmpls = append(tmpls, "templates/"+filePath)
+		tmpls = append(tmpls, prefix+filePath)
 	}
 	return tmpls
 }
 
-// HTMLRenderer returns a render.
-func HTMLRenderer() *render.Render {
-	return render.New(render.Options{
-		Extensions:                []string{".tmpl"},
-		Directory:                 "templates",
-		Funcs:                     NewFuncMap(),
-		Asset:                     GetAsset,
-		AssetNames:                GetAssetNames,
-		IsDevelopment:             !setting.IsProd,
-		DisableHTTPErrorRendering: true,
-	})
+func walkAssetDir(root string, skipMail bool, callback func(path, name string, d fs.DirEntry, err error) error) error {
+	mailRoot := filepath.Join(root, "mail")
+	if err := filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
+		name := path[len(root):]
+		if len(name) > 0 && name[0] == '/' {
+			name = name[1:]
+		}
+		if err != nil {
+			if os.IsNotExist(err) {
+				return callback(path, name, d, err)
+			}
+			return err
+		}
+		if skipMail && path == mailRoot && d.IsDir() {
+			return fs.SkipDir
+		}
+		if util.CommonSkip(d.Name()) {
+			if d.IsDir() {
+				return fs.SkipDir
+			}
+			return nil
+		}
+		if strings.HasSuffix(d.Name(), ".tmpl") || d.IsDir() {
+			return callback(path, name, d, err)
+		}
+		return nil
+	}); err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("unable to get files for template assets in %s: %w", root, err)
+	}
+	return nil
 }