Readonly mode doesn't disallow undo, replace, retab...

[dmaluka]

Description of the problem or steps to reproduce

Read-only mode (enabled via readonly option) doesn't fully disallow editing the buffer. It disables inserting and deleting text but doesn't disable at least the following operations:

• undo/redo
• replace
• retab
• comment/uncomment via comment plugin (since it uses Replace internally)

Specifications

Commit hash: ce46b8e OS: any Terminal: any

[Andriamanitra]

Adding autocomplete to the list of operations that are not disallowed. I ran into this issue while trying to use Readonly buffers as menus in a plugin.