Wiki does not merge commits

Summary

It the same Wiki page is open by 2 users the version saved by last one is kept, the other one disappear. Seems like Wiki pages are not really managed by git in terms of editing.

Steps to reproduce

1. Create Wiki page.
2. Edit page as user 1.
3. Using diffrent browser edit page as user 2.
4. User 1 make changes.
5. User 2 make changes.
6. User 1 save page.
7. User 2 save page.

What is the current bug behavior?

Changes of first user to save are lost.

What is the expected correct behavior?

Changes are merged or Wiki page not available to edit (locked) if other user is editing it.

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

Results of GitLab application Check

Possible fixes

Lock Wiki page during Edit.