[UPGRADE] run sanity checks before the database is upgraded

(cherry picked from commit 69741e4e66)
(cherry picked from commit 2a3c7b09cb)
(cherry picked from commit a1554c1168)
(cherry picked from commit edae2c6d2d)
(cherry picked from commit 49737cf009)
(cherry picked from commit ec53704c34)

models/migrations/migrations.go

@@ -28,6 +28,7 @@ import (
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
+	forgejo_services "code.gitea.io/gitea/services/forgejo"
 
 	"xorm.io/xorm"
 	"xorm.io/xorm/names"
@@ -591,6 +592,7 @@ func Migrate(x *xorm.Engine) error {
 		return fmt.Errorf("sync: %w", err)
 	}
 
+	var previousVersion int64
 	currentVersion := &Version{ID: 1}
 	has, err := x.Get(currentVersion)
 	if err != nil {
@@ -604,6 +606,8 @@ func Migrate(x *xorm.Engine) error {
 		if _, err = x.InsertOne(currentVersion); err != nil {
 			return fmt.Errorf("insert: %w", err)
 		}
+	} else {
+		previousVersion = currentVersion.Version
 	}
 
 	v := currentVersion.Version
@@ -631,6 +635,10 @@ Please try upgrading to a lower version first (suggested v1.6.4), then upgrade t
 		}
 	}
 
+	if err := forgejo_services.PreMigrationSanityChecks(x, previousVersion, setting.CfgProvider); err != nil {
+		return err
+	}
+
 	// Migrate
 	for i, m := range migrations[v-minDBVersion:] {
 		log.Info("Migration[%d]: %s", v+int64(i), m.Description())

services/forgejo/main_test.go

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: MIT
+
+package forgejo
+
+import (
+	"path/filepath"
+	"testing"
+
+	"code.gitea.io/gitea/models/unittest"
+
+	_ "code.gitea.io/gitea/models"
+	_ "code.gitea.io/gitea/models/actions"
+	_ "code.gitea.io/gitea/models/activities"
+)
+
+func TestMain(m *testing.M) {
+	unittest.MainTest(m, &unittest.TestOptions{
+		GiteaRootPath: filepath.Join("..", ".."),
+	})
+}

services/forgejo/sanity.go

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: MIT
+
+package forgejo
+
+import (
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+)
+
+var (
+	ForgejoV5DatabaseVersion = int64(260)
+	ForgejoV4DatabaseVersion = int64(244)
+)
+
+var logFatal = log.Fatal
+
+func fatal(err error) error {
+	logFatal("%v", err)
+	return err
+}
+
+func PreMigrationSanityChecks(e db.Engine, dbVersion int64, cfg setting.ConfigProvider) error {
+	return nil
+}

services/forgejo/sanity_test.go

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+
+package forgejo
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/unittest"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestForgejo_PreMigrationSanityChecks(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	ctx := db.DefaultContext
+	e := db.GetEngine(ctx)
+
+	assert.NoError(t, PreMigrationSanityChecks(e, ForgejoV4DatabaseVersion, configFixture(t, "")))
+}
+
+func configFixture(t *testing.T, content string) setting.ConfigProvider {
+	config := filepath.Join(t.TempDir(), "app.ini")
+	assert.NoError(t, os.WriteFile(config, []byte(content), 0o777))
+	cfg, err := setting.NewConfigProviderFromFile(config)
+	assert.NoError(t, err)
+	return cfg
+}