MergeRequests::PushOptionsHandlerService has been updated to allow
creating and updating merge requests with the
`merge_when_pipeline_succeeds` set using git push options.
To create a new merge request and set it to merge when the pipeline
succeeds:
git push -u origin -o merge_request.create \
-o merge_request.merge_when_pipeline_succeeds
To update an existing merge request and set it to merge when the
pipeline succeeds:
git push -u origin -o merge_request.merge_when_pipeline_succeeds
Issue https://gitlab.com/gitlab-org/gitlab-ce/issues/53198