Add template selection to git push options
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It would be nice to add an option to choose an MR template when creating a merge request using Git push options https://docs.gitlab.com/ee/user/project/push_options.html#push-options-for-merge-requests. For example:
```sh
git push \
-o merge_request.create \
-o merge_request.template=".gitlab/merge_requests_templates/template.md"
```
issue