Unity3D Editor script for warning about objects auto-setting the scene dirty right after saving it (looking at you, ContentSizeFitter)

SceneDirtyFlagChecker.cs

using System;
using System.Collections.Generic;
using UnityEditor;
using UnityEditor.SceneManagement;
using UnityEngine;
using UnityEngine.SceneManagement;

[InitializeOnLoad]
public class SceneDirtyFlagChecker
{
    private static Dictionary<Scene, DateTime> _sceneSavedTimestampMap = new Dictionary<Scene, DateTime>();

    static SceneDirtyFlagChecker()
    {
        Undo.postprocessModifications += OnPostProcessModifications;
        EditorSceneManager.sceneSaved += EditorSceneManager_sceneSaved;
    }

    private static void EditorSceneManager_sceneSaved(Scene scene)
    {
        _sceneSavedTimestampMap[scene] = DateTime.Now;
    }

    private static UndoPropertyModification[] OnPostProcessModifications(UndoPropertyModification[] propertyModifications)
    {
        if (Application.isPlaying)
            return propertyModifications;

        for (int i = 0; i < propertyModifications.Length; i++)
        {
            Scene? scene = null;
            switch (propertyModifications[i].currentValue.target)
            {
                case Component comp:
                    scene = comp.gameObject.scene;
                    break;

                case GameObject go:
                    scene = go.scene;
                    break;
            }

            if (scene.HasValue && _sceneSavedTimestampMap.TryGetValue(scene.Value, out DateTime timestamp))
            {
                if ((DateTime.Now - timestamp).TotalSeconds < 1)
                    Debug.LogWarning($"Object set scene dirty right after save: {propertyModifications[i].currentValue.target})\nYou can ignore this if the change was done manually.", propertyModifications[i].currentValue.target);
            }
        }

        return propertyModifications;
    }
}