update documents about LANGS

Author: wxiaoguang

custom/conf/app.example.ini

@@ -2117,6 +2117,7 @@ PATH =
 ;[i18n]
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; The first locale will be used as the default if user browser's language doesn't match any locale in the list.
 ;LANGS = en-US,zh-CN,zh-HK,zh-TW,de-DE,fr-FR,nl-NL,lv-LV,ru-RU,uk-UA,ja-JP,es-ES,pt-BR,pt-PT,pl-PL,bg-BG,it-IT,fi-FI,tr-TR,cs-CZ,sr-SP,sv-SE,ko-KR,el-GR,fa-IR,hu-HU,id-ID,ml-IN
 ;NAMES = English,简体中文,繁體中文（香港）,繁體中文（台灣）,Deutsch,français,Nederlands,latviešu,русский,Українська,日本語,español,português do Brasil,Português de Portugal,polski,български,italiano,suomi,Türkçe,čeština,српски,svenska,한국어,ελληνικά,فارسی,magyar nyelv,bahasa Indonesia,മലയാളം
 

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -997,7 +997,8 @@ Default templates for project boards:
 
 ## i18n (`i18n`)
 
-- `LANGS`: **en-US,zh-CN,zh-HK,zh-TW,de-DE,fr-FR,nl-NL,lv-LV,ru-RU,ja-JP,es-ES,pt-BR,pt-PT,pl-PL,bg-BG,it-IT,fi-FI,tr-TR,cs-CZ,sr-SP,sv-SE,ko-KR,el-GR,fa-IR,hu-HU,id-ID,ml-IN**: List of locales shown in language selector
+- `LANGS`: **en-US,zh-CN,zh-HK,zh-TW,de-DE,fr-FR,nl-NL,lv-LV,ru-RU,ja-JP,es-ES,pt-BR,pt-PT,pl-PL,bg-BG,it-IT,fi-FI,tr-TR,cs-CZ,sr-SP,sv-SE,ko-KR,el-GR,fa-IR,hu-HU,id-ID,ml-IN**:
+     List of locales shown in language selector. The first locale will be used as the default if user browser's language doesn't match any locale in the list.
 - `NAMES`: **English,简体中文,繁體中文（香港）,繁體中文（台灣）,Deutsch,français,Nederlands,latviešu,русский,日本語,español,português do Brasil,Português de Portugal,polski,български,italiano,suomi,Türkçe,čeština,српски,svenska,한국어,ελληνικά,فارسی,magyar nyelv,bahasa Indonesia,മലയാളം**: Visible names corresponding to the locales
 
 ## U2F (`U2F`) **DEPRECATED**

docs/content/doc/advanced/customizing-gitea.en-us.md

@@ -299,6 +299,8 @@ LANGS = en-US,foo-BAR
 NAMES = English,FooBar
 ```
 
+The first locale will be used as the default if user browser's language doesn't match any locale in the list.
+
 Locales may change between versions, so keeping track of your customized locales is highly encouraged.
 
 ### Readmes

modules/translation/translation.go

@@ -81,8 +81,11 @@ func InitLocales() {
 		}
 	}
 	if len(setting.Langs) != 0 {
-		log.Info("Use the first language (%s) in LANGS setting option as default language", setting.Langs[0])
-		i18n.DefaultLocales.SetDefaultLang(setting.Langs[0])
+		defaultLangName := setting.Langs[0]
+		if defaultLangName != "en-US" {
+			log.Info("Use the first locale (%s) in LANGS setting option as default", defaultLangName)
+		}
+		i18n.DefaultLocales.SetDefaultLang(defaultLangName)
 	}
 
 	langs, descs := i18n.DefaultLocales.ListLangNameDesc()