Push Option for Merge Request Dependency
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### Proposal
Our release pipeline makes use of the [Push Options for Merge Requests](https://docs.gitlab.com/ee/user/project/push_options.html#push-options-for-merge-requests), but its lacking an Option for setting a [Merge Request Dependency](https://docs.gitlab.com/ee/user/project/merge_requests/merge_request_dependencies.html)
Use case here is that we have an upstream project pipeline (with an MR) triggering a downstream project (creating an MR). As such, the downstream MR should not merge until the upstream merges. If I can pass the MR info from the upstream to the downstream, then I could additionally create the MR dependency with something like:
```
downstream-job:
...
script:
- ...
- |
git push --set-upstream origin "$BRANCH_NAME" \
-o merge_request.create \
-o merge_request.target=master \
-o merge_request.remove_source_branch \
-o merge_request.title="Release Candidate $RELEASE_VERSION" \
-o merge_request.dependency="$UPSTREAM_PROJECT_PATH/$UPSTREAM_MERGE_REQUEST_ID"
```
While this is our specific use case, this Push Option is flexible for many cases that involve creating an MR.
issue