Push option merge_request.(un)assign seems to be ignored

Summary

It seems that as well on gitlab.com as in our self-hosted GitLab 13.9.3-ee the push-options merge_request.assign and merge_request.unassign seem to be ignored.

Steps to reproduce

• Create a new repository
• Initialise the repo with a README
• Clone the repository
• Run git checkout -B test && date > test && git add test && git commit -m "Test" && git push -o merge_request.create -o merge_request.unassign="<current-users-username>" -o merge_request.assign="<another-users-username>"
• The merge request is created successfully but assigned to <current-users-username> instead of <another-users-username>

Example Project

https://gitlab.com/sventschui/testtest

What is the current bug behavior?

The merge request is assigned to <current-users-username>

What is the expected correct behavior?

The merge request is assigned to <another-users-username>

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

n/a

Results of GitLab application Check

n/a

Possible fixes

Workaround

As such git push -o commands are often used in scripts, creation of an MR could be followed-up by a call to the Update MR API to (un)set the assignee(s).