Only rename a user when they should receive a different name (#32247) (#32249)

Backport #32247 by @lunny

Fix #31996

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

services/user/user.go

@@ -32,6 +32,10 @@ import (
 
 // RenameUser renames a user
 func RenameUser(ctx context.Context, u *user_model.User, newUserName string) error {
+	if newUserName == u.Name {
+		return nil
+	}
+
 	// Non-local users are not allowed to change their username.
 	if !u.IsOrganization() && !u.IsLocal() {
 		return user_model.ErrUserIsNotLocal{
@@ -40,10 +44,6 @@ func RenameUser(ctx context.Context, u *user_model.User, newUserName string) err
 		}
 	}
 
-	if newUserName == u.Name {
-		return nil
-	}
-
 	if err := user_model.IsUsableUsername(newUserName); err != nil {
 		return err
 	}