Split migrations folder (#21549)

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

models/migrations/v1_11/v112.go

@@ -0,0 +1,48 @@
+// Copyright 2019 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_11 //nolint
+
+import (
+	"fmt"
+	"path/filepath"
+
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
+
+	"xorm.io/builder"
+	"xorm.io/xorm"
+)
+
+func RemoveAttachmentMissedRepo(x *xorm.Engine) error {
+	type Attachment struct {
+		UUID string `xorm:"uuid"`
+	}
+	var start int
+	attachments := make([]*Attachment, 0, 50)
+	for {
+		err := x.Select("uuid").Where(builder.NotIn("release_id", builder.Select("id").From("`release`"))).
+			And("release_id > 0").
+			OrderBy("id").Limit(50, start).Find(&attachments)
+		if err != nil {
+			return err
+		}
+
+		for i := 0; i < len(attachments); i++ {
+			uuid := attachments[i].UUID
+			if err = util.RemoveAll(filepath.Join(setting.Attachment.Path, uuid[0:1], uuid[1:2], uuid)); err != nil {
+				fmt.Printf("Error: %v", err)
+			}
+		}
+
+		if len(attachments) < 50 {
+			break
+		}
+		start += 50
+		attachments = attachments[:0]
+	}
+
+	_, err := x.Exec("DELETE FROM attachment WHERE release_id > 0 AND release_id NOT IN (SELECT id FROM `release`)")
+	return err
+}