Preserve threads where the parent comment was deleted
<!-- The first four sections: "Problem to solve", "Intended users", "User experience goal", and "Proposal", are strongly recommended, while the rest of the sections can be filled out during the problem validation or breakdown phase. However, keep in mind that providing complete and relevant information early helps our product team validate the problem and start working on a solution. --> ### Problem to solve Currently, when you start a thread on the merge request "changes" tab, or when you start a thread as an issue or merge request comment, then delete the comment that started the thread, the child comments get realigned to a new parent (the second comment in the thread) This is a problem because the context of the discussion itself is changed. If the discussion has started due to a particular comment, and that comment no longer exists, then the child comments become somewhat irrelevant. For example: | Before deleting the parent | After deleting the parent | | ------ | ------ | | ![Screen_Shot_2020-06-23_at_10.38.15_AM](/uploads/cc7d8c9fc6c024d55a1ac4019110de92/Screen_Shot_2020-06-23_at_10.38.15_AM.png) | ![Screen_Shot_2020-06-23_at_10.38.29_AM](/uploads/ba7adada95a59c3c3f83a1a2e771b86d/Screen_Shot_2020-06-23_at_10.38.29_AM.png) | The context in the above examples has now changed drastically and we are no longer being transparent about the original discussion. This has recently come to light with the new releases from the [merge ref comparison mode epic](https://gitlab.com/groups/gitlab-org/-/epics/854), particularly because [we still need to handle this circumstance when comparing against merge(head)](https://gitlab.com/gitlab-org/gitlab/-/issues/213854). The proposal on that issue is currently to keep the functionality the same as it is today, but we should instead evaluate whether it is correct today. As a user, I want to see that there used to be a different parent comment on a thread, so that I can understand the context of the children comments. <!-- What problem do we solve? Try to define the who/what/why of the opportunity as a user story. For example, "As a (who), I want (what), so I can (why/value)." --> ### Intended users <!-- Who will use this feature? If known, include any of the following: types of users (e.g. Developer), personas, or specific company roles (e.g. Release Manager). It's okay to write "Unknown" and fill this field in later. Personas are described at https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/ * [Cameron (Compliance Manager)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#cameron-compliance-manager) * [Parker (Product Manager)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#parker-product-manager) * [Delaney (Development Team Lead)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#delaney-development-team-lead) * [Presley (Product Designer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#presley-product-designer) * [Sasha (Software Developer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sasha-software-developer) * [Devon (DevOps Engineer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#devon-devops-engineer) * [Sidney (Systems Administrator)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sidney-systems-administrator) * [Sam (Security Analyst)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sam-security-analyst) * [Rachel (Release Manager)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#rachel-release-manager) * [Alex (Security Operations Engineer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#alex-security-operations-engineer) * [Simone (Software Engineer in Test)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#simone-software-engineer-in-test) * [Allison (Application Ops)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#allison-application-ops) * [Priyanka (Platform Engineer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#priyanka-platform-engineer) * [Dana (Data Analyst)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#dana-data-analyst) --> ### User experience goal <!-- What is the single user experience workflow this problem addresses? For example, "The user should be able to use the UI/API/.gitlab-ci.yml with GitLab to <perform a specific task>" https://about.gitlab.com/handbook/engineering/ux/ux-research-training/user-story-mapping/ --> ### Proposal <!-- How are we going to solve the problem? Try to include the user journey! https://about.gitlab.com/handbook/journeys/#user-journey --> @andr3 has proposed a valid option, which is to keep the parent comment in tact, but remove the user data, and change the text to indicate that it's been deleted: ![Screen_Shot_2020-06-23_at_10.45.29_AM](/uploads/984add7e467126cb9ad2d2b36250f984/Screen_Shot_2020-06-23_at_10.45.29_AM.png) ### Further details <!-- Include use cases, benefits, goals, or any other details that will help us understand the problem better. --> ### Permissions and Security <!-- What permissions are required to perform the described actions? Are they consistent with the existing permissions as documented for users, groups, and projects as appropriate? Is the proposed behavior consistent between the UI, API, and other access methods (e.g. email replies)?--> ### Documentation <!-- See the Feature Change Documentation Workflow https://docs.gitlab.com/ee/development/documentation/workflow.html#for-a-product-change * Add all known Documentation Requirements in this section. See https://docs.gitlab.com/ee/development/documentation/feature-change-workflow.html#documentation-requirements * If this feature requires changing permissions, update the permissions document. See https://docs.gitlab.com/ee/user/permissions.html --> ### Availability & Testing <!-- This section needs to be retained and filled in during the workflow planning breakdown phase of this feature proposal, if not earlier. What risks does this change pose to our availability? How might it affect the quality of the product? What additional test coverage or changes to tests will be needed? Will it require cross-browser testing? Please list the test areas (unit, integration and end-to-end) that needs to be added or updated to ensure that this feature will work as intended. Please use the list below as guidance. * Unit test changes * Integration test changes * End-to-end test change See the test engineering planning process and reach out to your counterpart Software Engineer in Test for assistance: https://about.gitlab.com/handbook/engineering/quality/test-engineering/#test-planning --> ### What does success look like, and how can we measure that? <!-- Define both the success metrics and acceptance criteria. Note that success metrics indicate the desired business outcomes, while acceptance criteria indicate when the solution is working correctly. If there is no way to measure success, link to an issue that will implement a way to measure this. --> ### What is the type of buyer? <!-- What is the buyer persona for this feature? See https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/buyer-persona/ In which enterprise tier should this feature go? See https://about.gitlab.com/handbook/product/pricing/#four-tiers --> ### Is this a cross-stage feature? <!-- Communicate if this change will affect multiple Stage Groups or product areas. We recommend always start with the assumption that a feature request will have an impact into another Group. Loop in the most relevant PM and Product Designer from that Group to provide strategic support to help align the Group's broader plan and vision, as well as to avoid UX and technical debt. https://about.gitlab.com/handbook/product/#cross-stage-features --> ### Links / references /cc @pedroms @igor.drozdov
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