Split migrations folder (#21549)

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

models/migrations/v1_15/v181.go

@@ -0,0 +1,93 @@
+// Copyright 2021 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_15 //nolint
+
+import (
+	"strings"
+
+	"xorm.io/xorm"
+)
+
+func AddPrimaryEmail2EmailAddress(x *xorm.Engine) (err error) {
+	type User struct {
+		ID       int64  `xorm:"pk autoincr"`
+		Email    string `xorm:"NOT NULL"`
+		IsActive bool   `xorm:"INDEX"` // Activate primary email
+	}
+
+	type EmailAddress1 struct {
+		ID          int64  `xorm:"pk autoincr"`
+		UID         int64  `xorm:"INDEX NOT NULL"`
+		Email       string `xorm:"UNIQUE NOT NULL"`
+		LowerEmail  string
+		IsActivated bool
+		IsPrimary   bool `xorm:"DEFAULT(false) NOT NULL"`
+	}
+
+	// Add lower_email and is_primary columns
+	if err = x.Table("email_address").Sync2(new(EmailAddress1)); err != nil {
+		return
+	}
+
+	if _, err = x.Exec("UPDATE email_address SET lower_email=LOWER(email), is_primary=?", false); err != nil {
+		return
+	}
+
+	type EmailAddress struct {
+		ID          int64  `xorm:"pk autoincr"`
+		UID         int64  `xorm:"INDEX NOT NULL"`
+		Email       string `xorm:"UNIQUE NOT NULL"`
+		LowerEmail  string `xorm:"UNIQUE NOT NULL"`
+		IsActivated bool
+		IsPrimary   bool `xorm:"DEFAULT(false) NOT NULL"`
+	}
+
+	// change lower_email as unique
+	if err = x.Sync2(new(EmailAddress)); err != nil {
+		return
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+
+	const batchSize = 100
+
+	for start := 0; ; start += batchSize {
+		users := make([]*User, 0, batchSize)
+		if err = sess.Limit(batchSize, start).Find(&users); err != nil {
+			return
+		}
+		if len(users) == 0 {
+			break
+		}
+
+		for _, user := range users {
+			var exist bool
+			exist, err = sess.Where("email=?", user.Email).Table("email_address").Exist()
+			if err != nil {
+				return
+			}
+			if !exist {
+				if _, err = sess.Insert(&EmailAddress{
+					UID:         user.ID,
+					Email:       user.Email,
+					LowerEmail:  strings.ToLower(user.Email),
+					IsActivated: user.IsActive,
+					IsPrimary:   true,
+				}); err != nil {
+					return
+				}
+			} else {
+				if _, err = sess.Where("email=?", user.Email).Cols("is_primary").Update(&EmailAddress{
+					IsPrimary: true,
+				}); err != nil {
+					return
+				}
+			}
+		}
+	}
+
+	return nil
+}