For the Mongosync project, we have many suites configured, each of which have large lists of excluded files and tags. Most suites have significant overlap in these lists, as there are some tests/tags that always fail in our suites. In other cases, the exclusions are shared between some but not all suites.

Right now we have no way to abstract these lists, so they end up repeated across many suites. Keeping these up to date when something needs to be added or removed from this list is tedious.

We'd like to be able to create a set of lists that we can then merge together in different combinations as part of the matrix suite generation. Right now this isn't possible as the matrix suite only allows overrides, which simply replace an existing YAML key wholesale.

See REP-576 for a more detailed discussion of the suites we have and how we're trying to simplify them.