You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: v139.go
    path of file: ./repos/gitea/models/migrations/v1_12
    
    the code of the file until where you have to start completion: // Copyright 2019 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package v1_12 //nolint

import (
	"code.gitea.io/gitea/modules/setting"

	"xorm.io/xorm"
)

func PrependRefsHeadsToIssueRefs(x *xorm.Engine) error {
	var query string

	switch {
	case setting.Database.Type.IsMSSQL():
		query = "UPDATE `issue` SET `ref` = 'refs/heads/' + `ref` WHERE `ref` IS NOT NULL AND `ref` <> '' AND `ref` NOT LIKE 'refs/%'"
	case setting.Database.Type.IsMySQL():
		query = "UPDATE `issue` SET `ref` = CONCAT('refs/heads/', `ref`) WHERE `ref` IS NOT NULL AND
    
func PrependRefsHeadsToIssueRefs(x *xorm.Engine) error {
	var query string

	switch {
	case setting.Database.Type.IsMSSQL():
		query = "UPDATE `issue` SET `ref` = 'refs/heads/' + `ref` WHERE `ref` IS NOT NULL AND `ref` <> '' AND `ref` NOT LIKE 'refs/%'"
	case setting.Database.Type.IsMySQL():
		query = "UPDATE `issue` SET `ref` = CONCAT('refs/heads/', `ref`) WHERE `ref` IS NOT NULL AND `ref` <> '' AND `ref` NOT LIKE 'refs/%';"
	default:
		query = "UPDATE `issue` SET `ref` = 'refs/heads/' || `ref` WHERE `ref` IS NOT NULL AND `ref` <> '' AND `ref` NOT LIKE 'refs/%'"
	}

	_, err := x.Exec(query)
	return err
}