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/v140.go

@@ -0,0 +1,57 @@
+// 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 (
+	"fmt"
+
+	"code.gitea.io/gitea/models/migrations/base"
+	"code.gitea.io/gitea/modules/setting"
+
+	"xorm.io/xorm"
+)
+
+func FixLanguageStatsToSaveSize(x *xorm.Engine) error {
+	// LanguageStat see models/repo_language_stats.go
+	type LanguageStat struct {
+		Size int64 `xorm:"NOT NULL DEFAULT 0"`
+	}
+
+	// RepoIndexerType specifies the repository indexer type
+	type RepoIndexerType int
+
+	const (
+		// RepoIndexerTypeCode code indexer
+		RepoIndexerTypeCode RepoIndexerType = iota // 0
+		// RepoIndexerTypeStats repository stats indexer
+		RepoIndexerTypeStats // 1
+	)
+
+	// RepoIndexerStatus see models/repo_indexer.go
+	type RepoIndexerStatus struct {
+		IndexerType RepoIndexerType `xorm:"INDEX(s) NOT NULL DEFAULT 0"`
+	}
+
+	if err := x.Sync2(new(LanguageStat)); err != nil {
+		return fmt.Errorf("Sync2: %w", err)
+	}
+
+	x.Delete(&RepoIndexerStatus{IndexerType: RepoIndexerTypeStats})
+
+	// Delete language stat statuses
+	truncExpr := "TRUNCATE TABLE"
+	if setting.Database.UseSQLite3 {
+		truncExpr = "DELETE FROM"
+	}
+
+	// Delete language stats
+	if _, err := x.Exec(fmt.Sprintf("%s language_stat", truncExpr)); err != nil {
+		return err
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+	return base.DropTableColumns(sess, "language_stat", "percentage")
+}