auth: redirect landing URL with subpath prepended (#5964)

conf/app.ini

@@ -52,7 +52,8 @@ APP_DATA_PATH = data
 ; Whether to enable to load assets (i.e. "conf", "templates", "public") from disk instead of embedded bindata.
 LOAD_ASSETS_FROM_DISK = false
 
-; The landing page URL for anonymous users, can be a link to a external site.
+; The landing page URL for anonymous users, the value should not include
+; subpath that is handled by the reverse proxy.
 LANDING_URL = /
 
 ; Whether to disable SSH access to the application entirely.

internal/context/auth.go

@@ -41,7 +41,7 @@ func Toggle(options *ToggleOptions) macaron.Handler {
 
 		// Check non-logged users landing page.
 		if !c.IsLogged && c.Req.RequestURI == "/" && conf.Server.LandingURL != "/" {
-			c.Redirect(conf.Server.LandingURL)
+			c.SubURLRedirect(conf.Server.LandingURL)
 			return
 		}