Add test for ExtendCommentTreePathLength migration and fix bugs (#35791)

Co-authored-by: Mithilesh Gupta <guptamithilesh@protonmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

models/migrations/v1_25/v322_test.go

@@ -0,0 +1,34 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_25
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/migrations/base"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_ExtendCommentTreePathLength(t *testing.T) {
+	if setting.Database.Type.IsSQLite3() {
+		t.Skip("For SQLITE, varchar or char will always be represented as TEXT")
+	}
+
+	type Comment struct {
+		ID       int64  `xorm:"pk autoincr"`
+		TreePath string `xorm:"VARCHAR(255)"`
+	}
+
+	x, deferrable := base.PrepareTestEnv(t, 0, new(Comment))
+	defer deferrable()
+
+	require.NoError(t, ExtendCommentTreePathLength(x))
+	table := base.LoadTableSchemasMap(t, x)["comment"]
+	column := table.GetColumn("tree_path")
+	assert.Contains(t, []string{"NVARCHAR", "VARCHAR"}, column.SQLType.Name)
+	assert.EqualValues(t, 4000, column.Length)
+}