Meta-Issues: Allow the building for a issue hierachry

Description

Allow issues (so called meta-issues) to reference other issues (so called sub-issues) or alternatively other milestones (so called sub-milestones). A parent-child association is created and all linked sub-issues are listed with their state in the meta-issue view.

Proposal

The current set of features like issues, boards, milestones and labels allow us to create a rather flat organisation of issues. That's OK for many agile or collaborative project management flows. More difficult flows can be organized by creating so called meta-issues.

A meta-issue is an issue linking to sub-issues. It contains a checkbox list with links to all sub-issues. If a sub-issue is closed, the checkbox in the meta-issue is checked. If all sub-issues are closed, the meta-issue get's closed too.

Currently, this flow needs a lot of manual work:

1. Create a meta issue -> can't be automated, someone needs to type e.g. the title
2. Create a checkbox list of sub-issues -> can be created from the parent-child association
3. Update the checkbox list, if new issues are assigned to an existing meta-issue -> the sub-issue state can be reflected as a checkbox state
4. Check if all sub-issues are closed and manually close the meta-issue -> changing the state of a sub-issue triggers a check in the corresponding meta-issue

Alternative

An alternative, but similar flow could use meta-issues and sub-milestones. In that case, all tasks are organized in a sub-milestone. Each sub-milestone has a corresponding meta-issue, which is in turn organized in a (parent-)milestone.

So in that scenario, a meta-issue is linked to milestone and the state of a meta-issue (open ... closed) is corresponding to the state of a milestone. This should also include the due date. So by creating a milestone and setting the kind to "sub-milestone", a new meta-issue is created containing the same title and due date. The meta-issue can now be assigned to a parent-milestone.

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Hier is an example hierarchy of tasks:

• Some day maybe
  • Implement unlimited integer types
• VHDL-2020
  • Integrate proposed language changes
    • Implement derived integer types
    • Implement derived enumeration types
  • Review existing code
    • Create a style guide
    • Apply the style guide to all packages
    • Remove dead code
    • Review all code comments
    • Comment all uncommented subprograms
• VHDL-2017
  • Integrate proposed language changes
    • LCS-001
    • LCS-002
    • ...
    • LCS-095
  • Review existing code
    • Update page references in all packages

Related issues:

• #2001 (closed)

@paebbels It's similar to the "Related Issues" work which is ongoing in the following issue:

• https://gitlab.com/gitlab-org/gitlab-ee/issues/2001

/cc @victorwu

added ~874214 feature proposal ~155959 labels

@paebbels That feature is scheduled for v9.3 release this month

changed the description

@markglenfletcher Yes it's related to #2001 (closed), but I think my proposal has more benefits then just adding related issues in a list. In my idea, the meta-issue is closed automatically (or a user is notified that an action is required / can be performed), based on the aggregated status of all sub-issues. While #2001 (closed) is a step into the right direction, I think my proposal could created less work for a "board moderator".

changed the description