Subgroups are not supported in mySQL. I changed Namespace#root_ancestor
to return from self_and_ancestors as a bugfix.
```
184 # Returns all the ancestors of the current namespaces
185 def ancestors
186 return self.class.none unless parent_id
187
188 Gitlab::GroupHierarchy
189 .new(self.class.where(id: parent_id))
190 .base_and_ancestors
191 end
```
So it seems like on mySQL we accidentally returned the parent group :
```
ancestors = self.class.where(id: parent_id)
ancestors.reorder(nil).find_by(parent_id: nil)
```
Project#root_namespace is used only by shared_runners_limit_namespace
and all the tests for shared_runner_minutes_on_root_namespace are only
enabled on `:nested_groups`
`when :shared_runner_minutes_on_root_namespace is enabled', :nested_groups`
We very clearly state in https://docs.gitlab.com/ee/user/group/subgroups/ that `
Nested groups are only supported when you use PostgreSQL`, so I think I
will fix forward and add `:nested_groups` to the two failing feature
specs.
