Split migrations folder (#21549)

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

models/migrations/v1_10/v96.go

@@ -0,0 +1,65 @@
+// 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_10 //nolint
+
+import (
+	"path/filepath"
+
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
+
+	"xorm.io/xorm"
+)
+
+func DeleteOrphanedAttachments(x *xorm.Engine) error {
+	type Attachment struct {
+		ID        int64  `xorm:"pk autoincr"`
+		UUID      string `xorm:"uuid UNIQUE"`
+		IssueID   int64  `xorm:"INDEX"`
+		ReleaseID int64  `xorm:"INDEX"`
+		CommentID int64
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+
+	limit := setting.Database.IterateBufferSize
+	if limit <= 0 {
+		limit = 50
+	}
+
+	for {
+		attachements := make([]Attachment, 0, limit)
+		if err := sess.Where("`issue_id` = 0 and (`release_id` = 0 or `release_id` not in (select `id` from `release`))").
+			Cols("id, uuid").Limit(limit).
+			Asc("id").
+			Find(&attachements); err != nil {
+			return err
+		}
+		if len(attachements) == 0 {
+			return nil
+		}
+
+		ids := make([]int64, 0, limit)
+		for _, attachment := range attachements {
+			ids = append(ids, attachment.ID)
+		}
+		if len(ids) > 0 {
+			if _, err := sess.In("id", ids).Delete(new(Attachment)); err != nil {
+				return err
+			}
+		}
+
+		for _, attachment := range attachements {
+			uuid := attachment.UUID
+			if err := util.RemoveAll(filepath.Join(setting.Attachment.Path, uuid[0:1], uuid[1:2], uuid)); err != nil {
+				return err
+			}
+		}
+		if len(attachements) < limit {
+			return nil
+		}
+	}
+}