Merge materials similar like Purge

There is issue where materials are duplicated and after this often not used

• blender.stackexchange.com/questions/75790/how-to-merge-around-300-duplicate-materials
• youtu.be/bIob1Mgblm0
• youtu.be/Wr6nyqj1CRM

I think that user should have:

• Purge material but after checkbox selected
• Merge materials but after checkbox selected

Both options should have be in File > Clean up