Fix recovery middleware to render gitea style page. (#13857)

* Some changes to fix recovery

* Move Recovery to middlewares

* Remove trace code

* Fix lint

* add session middleware and remove dependent on macaron for sso

* Fix panic 500 page rendering

* Fix bugs

* Fix fmt

* Fix vendor

* recover unnecessary change

* Fix lint and addd some comments about the copied codes.

* Use util.StatDir instead of com.StatDir

Co-authored-by: 6543 <6543@obermui.de>

modules/middlewares/locale.go

@@ -0,0 +1,49 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package middlewares
+
+import (
+	"net/http"
+
+	"code.gitea.io/gitea/modules/translation"
+
+	"github.com/unknwon/i18n"
+	"golang.org/x/text/language"
+)
+
+// Locale handle locale
+func Locale(resp http.ResponseWriter, req *http.Request) translation.Locale {
+	hasCookie := false
+
+	// 1. Check URL arguments.
+	lang := req.URL.Query().Get("lang")
+
+	// 2. Get language information from cookies.
+	if len(lang) == 0 {
+		ck, _ := req.Cookie("lang")
+		lang = ck.Value
+		hasCookie = true
+	}
+
+	// Check again in case someone modify by purpose.
+	if !i18n.IsExist(lang) {
+		lang = ""
+		hasCookie = false
+	}
+
+	// 3. Get language information from 'Accept-Language'.
+	// The first element in the list is chosen to be the default language automatically.
+	if len(lang) == 0 {
+		tags, _, _ := language.ParseAcceptLanguage(req.Header.Get("Accept-Language"))
+		tag, _, _ := translation.Match(tags...)
+		lang = tag.String()
+	}
+
+	if !hasCookie {
+		req.AddCookie(NewCookie("lang", lang, 1<<31-1))
+	}
+
+	return translation.NewLocale(lang)
+}