Split migrations folder (#21549)

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

models/migrations/base/db_test.go

@@ -0,0 +1,97 @@
+// 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 base
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm/names"
+)
+
+func Test_DropTableColumns(t *testing.T) {
+	x, deferable := PrepareTestEnv(t, 0)
+	if x == nil || t.Failed() {
+		defer deferable()
+		return
+	}
+	defer deferable()
+
+	type DropTest struct {
+		ID            int64 `xorm:"pk autoincr"`
+		FirstColumn   string
+		ToDropColumn  string `xorm:"unique"`
+		AnotherColumn int64
+		CreatedUnix   timeutil.TimeStamp `xorm:"INDEX created"`
+		UpdatedUnix   timeutil.TimeStamp `xorm:"INDEX updated"`
+	}
+
+	columns := []string{
+		"first_column",
+		"to_drop_column",
+		"another_column",
+		"created_unix",
+		"updated_unix",
+	}
+
+	for i := range columns {
+		x.SetMapper(names.GonicMapper{})
+		if err := x.Sync2(new(DropTest)); err != nil {
+			t.Errorf("unable to create DropTest table: %v", err)
+			return
+		}
+		sess := x.NewSession()
+		if err := sess.Begin(); err != nil {
+			sess.Close()
+			t.Errorf("unable to begin transaction: %v", err)
+			return
+		}
+		if err := DropTableColumns(sess, "drop_test", columns[i:]...); err != nil {
+			sess.Close()
+			t.Errorf("Unable to drop columns[%d:]: %s from drop_test: %v", i, columns[i:], err)
+			return
+		}
+		if err := sess.Commit(); err != nil {
+			sess.Close()
+			t.Errorf("unable to commit transaction: %v", err)
+			return
+		}
+		sess.Close()
+		if err := x.DropTables(new(DropTest)); err != nil {
+			t.Errorf("unable to drop table: %v", err)
+			return
+		}
+		for j := range columns[i+1:] {
+			x.SetMapper(names.GonicMapper{})
+			if err := x.Sync2(new(DropTest)); err != nil {
+				t.Errorf("unable to create DropTest table: %v", err)
+				return
+			}
+			dropcols := append([]string{columns[i]}, columns[j+i+1:]...)
+			sess := x.NewSession()
+			if err := sess.Begin(); err != nil {
+				sess.Close()
+				t.Errorf("unable to begin transaction: %v", err)
+				return
+			}
+			if err := DropTableColumns(sess, "drop_test", dropcols...); err != nil {
+				sess.Close()
+				t.Errorf("Unable to drop columns: %s from drop_test: %v", dropcols, err)
+				return
+			}
+			if err := sess.Commit(); err != nil {
+				sess.Close()
+				t.Errorf("unable to commit transaction: %v", err)
+				return
+			}
+			sess.Close()
+			if err := x.DropTables(new(DropTest)); err != nil {
+				t.Errorf("unable to drop table: %v", err)
+				return
+			}
+		}
+	}
+}