Warn when merging an MR related to a blocked issue
Release notes
Problem to solve
When completing dependent work in parallel it's possible to merge a change before its dependency if the author doesn't know to set an MR dependency. However, we can infer a dependency from related blocking users and warn the person performing the merge.
Intended users
User experience goal
The merging user is alerted to a possible dependency before merging an MR.
Proposal
An MR dependency could be automatically created, however that would involve joining MRs of a blocking issue with those of its blocker - which could be difficult. It's easier just to identify a related issue as blocked by an open issue and unobtrusively warn the user before a merge.
Further details
A concrete example of this created a production incident for GitLab. See gitlab-com/gl-infra/production#3267 (closed).
In this case a community contributor didn't know to set the MR dependency and reviews were performed in isolation by separate reviewers/maintainers who were unaware of the dependency. The blocking relationship was defined in the related issues, #288715 (closed) and #226988 (closed).
Permissions and Security
Documentation
Availability & Testing
Available Tier
Blocking issues are in Core. If we go with a warning it can be in core too, if an MR dependency is used it would need to be in Premium.