📍 Merge request push option for "Merge at a scheduled date and time"
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### Release notes
<!-- What is the problem and solution you're proposing? This content sets the overall vision for the feature and serves as the release notes that will populate in various places, including the [release post blog](https://about.gitlab.com/releases/categories/releases/) and [Gitlab project releases](https://gitlab.com/gitlab-org/gitlab/-/releases). " -->
Folks who appreciate the ability to [Merge at a scheduled date and time](https://about.gitlab.com/releases/2024/11/21/gitlab-17-6-released/#merge-at-a-scheduled-date-and-time) can now make use of this functionality in [Push options for merge requests](https://docs.gitlab.com/ee/topics/git/commit.html#push-options-for-merge-requests).
### Problem to solve
<!-- What is the user problem you are trying to solve with this issue? -->
The ability [Merge at a scheduled date and time](https://about.gitlab.com/releases/2024/11/21/gitlab-17-6-released/#merge-at-a-scheduled-date-and-time) is a useful feature. Folks may wish to set the scheduled date and time in a merge request push option.
### Proposal
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Permit folks to create an MR that is configured to merge at a scheduled date and time with a command like:
```shell
git push -o mr.create -o merge_request.target=main -o merge_request.scheduled-merge=1732297061 -o merge_request.assign="bcarranza" -o merge_request.title="✨ Add information next month"
```
....where `1732297061` is the output of `date +%s`.
:sparkles: Some work remains to be done to figure out how folks would specify a timestamp.
### Intended users
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* [Delaney (Development Team Lead)](https://handbook.gitlab.com/handbook/product/personas/#delaney-development-team-lead)
* [Sasha (Software Developer)](https://handbook.gitlab.com/handbook/product/personas/#sasha-software-developer)
* [Rachel (Release Manager)](https://handbook.gitlab.com/handbook/product/personas/#rachel-release-manager)
* [Ingrid (Infrastructure Operator)](https://handbook.gitlab.com/handbook/product/personas/#ingrid-infrastructure-operator)
* [Dakota (Application Development Director)](https://handbook.gitlab.com/handbook/product/personas/#dakota-application-development-director)
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