Refactor the DB migration system slightly (#32344)

Introduce "idNumber" for each migration, and clarify the difference
between the migration ID number and database version.

models/migrations/migrations_test.go

@@ -0,0 +1,28 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package migrations
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/modules/test"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMigrations(t *testing.T) {
+	defer test.MockVariableValue(&preparedMigrations)()
+	preparedMigrations = []*migration{
+		{idNumber: 70},
+		{idNumber: 71},
+	}
+	assert.EqualValues(t, 72, calcDBVersion(preparedMigrations))
+	assert.EqualValues(t, 72, ExpectedDBVersion())
+
+	assert.EqualValues(t, 71, migrationIDNumberToDBVersion(70))
+
+	assert.EqualValues(t, []*migration{{idNumber: 70}, {idNumber: 71}}, getPendingMigrations(70, preparedMigrations))
+	assert.EqualValues(t, []*migration{{idNumber: 71}}, getPendingMigrations(71, preparedMigrations))
+	assert.EqualValues(t, []*migration{}, getPendingMigrations(72, preparedMigrations))
+}

routers/common/db.go

@@ -51,7 +51,7 @@ func migrateWithSetting(x *xorm.Engine) error {
 	} else if current < 0 {
 		// execute migrations when the database isn't initialized even if AutoMigration is false
 		return migrations.Migrate(x)
-	} else if expected := migrations.ExpectedVersion(); current != expected {
+	} else if expected := migrations.ExpectedDBVersion(); current != expected {
 		log.Fatal(`"database.AUTO_MIGRATION" is disabled, but current database version %d is not equal to the expected version %d.`+
 			`You can set "database.AUTO_MIGRATION" to true or migrate manually by running "gitea [--config /path/to/app.ini] migrate"`, current, expected)
 	}

services/doctor/dbversion.go

@@ -12,7 +12,7 @@ import (
 )
 
 func checkDBVersion(ctx context.Context, logger log.Logger, autofix bool) error {
-	logger.Info("Expected database version: %d", migrations.ExpectedVersion())
+	logger.Info("Expected database version: %d", migrations.ExpectedDBVersion())
 	if err := db.InitEngineWithMigration(ctx, migrations.EnsureUpToDate); err != nil {
 		if !autofix {
 			logger.Critical("Error: %v during ensure up to date", err)