Redmine

It would great if it was possible to assign multiple parent issues to a given issue.

If this was possible, one would be able to easily create arbitray subsets of issues.

As an example, suppose we have two things we want to make: We want to make a car and we want to make a bicycle. However, as a part of making both a car and a bicycle we need to invent the wheel. So, we create one issue for making the car, another issue for making the bicycle and finally an issue for inventing the wheel. The wheel issue then has both the bicycle and the car issues as parent.

Another example: Suppose there are various releases of some software. Each release could then have its own issue and each bug could then have the issues which it affects as parents.