Split migrations folder (#21549)

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

models/migrations/v1_18/v229.go

@@ -0,0 +1,47 @@
+// Copyright 2022 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_18 //nolint
+
+import (
+	"fmt"
+
+	"code.gitea.io/gitea/models/issues"
+
+	"xorm.io/builder"
+	"xorm.io/xorm"
+)
+
+func UpdateOpenMilestoneCounts(x *xorm.Engine) error {
+	var openMilestoneIDs []int64
+	err := x.Table("milestone").Select("id").Where(builder.Neq{"is_closed": 1}).Find(&openMilestoneIDs)
+	if err != nil {
+		return fmt.Errorf("error selecting open milestone IDs: %w", err)
+	}
+
+	for _, id := range openMilestoneIDs {
+		_, err := x.ID(id).
+			SetExpr("num_issues", builder.Select("count(*)").From("issue").Where(
+				builder.Eq{"milestone_id": id},
+			)).
+			SetExpr("num_closed_issues", builder.Select("count(*)").From("issue").Where(
+				builder.Eq{
+					"milestone_id": id,
+					"is_closed":    true,
+				},
+			)).
+			Update(&issues.Milestone{})
+		if err != nil {
+			return fmt.Errorf("error updating issue counts in milestone %d: %w", id, err)
+		}
+		_, err = x.Exec("UPDATE `milestone` SET completeness=100*num_closed_issues/(CASE WHEN num_issues > 0 THEN num_issues ELSE 1 END) WHERE id=?",
+			id,
+		)
+		if err != nil {
+			return fmt.Errorf("error setting completeness on milestone %d: %w", id, err)
+		}
+	}
+
+	return nil
+}