Split migrations folder (#21549)

There are too many files in `models/migrations` folder so that I split
them into sub folders.

models/migrations/v1_13/v143.go

@@ -0,0 +1,52 @@
+// 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 v1_13 //nolint
+
+import (
+	"code.gitea.io/gitea/modules/log"
+
+	"xorm.io/xorm"
+)
+
+func RecalculateStars(x *xorm.Engine) (err error) {
+	// because of issue https://github.com/go-gitea/gitea/issues/11949,
+	// recalculate Stars number for all users to fully fix it.
+
+	type User struct {
+		ID int64 `xorm:"pk autoincr"`
+	}
+
+	const batchSize = 100
+	sess := x.NewSession()
+	defer sess.Close()
+
+	for start := 0; ; start += batchSize {
+		users := make([]User, 0, batchSize)
+		if err = sess.Limit(batchSize, start).Where("type = ?", 0).Cols("id").Find(&users); err != nil {
+			return
+		}
+		if len(users) == 0 {
+			break
+		}
+
+		if err = sess.Begin(); err != nil {
+			return
+		}
+
+		for _, user := range users {
+			if _, err = sess.Exec("UPDATE `user` SET num_stars=(SELECT COUNT(*) FROM `star` WHERE uid=?) WHERE id=?", user.ID, user.ID); err != nil {
+				return
+			}
+		}
+
+		if err = sess.Commit(); err != nil {
+			return
+		}
+	}
+
+	log.Debug("recalculate Stars number for all user finished")
+
+	return err
+}