Undo unavailable after inserting template before editing content

[damo]

1. Open editor (do not edit content)
   
2. Use template button to insert any template with "Replace content" option active.
   

Result: Undo is not available

[garry.yao]

Adding snapshots for inserting templates with replace mode.

[alfonsoml]

Wouldn't it be better to add the save snapshots inside the setData?

Any plugin or external code that modifies the content will have to be aware of this behavior, I don't think that it's straightforward that people is required to save a snapshot themselves when they are calling an API to alter the content of the editor.

[garry.yao]

Replying to alfonsoml: Definitely, nice prompt.

[garry.yao]

Fixed with [5015].

[fredck]

I've just reverted [5015]. It's causing several issues with the undo system (e.g. #5191 and #5208).

[fredck]

Btw, reverted with [5163].

[fredck]

I understand that having the undo snapshot for setData is needed, but it looks like there is much more work to have it working properly. I've opened #5217 for it, while still fixing this ticket with the first patch provided by Garry, with [5166].