Comment 7 for bug 1296913

Proposed solution to be backwards compatible:

1) if group=foo is specified and group 'foo' does not exist, automatically create it. Set a special policy type of "scheduler" on the automatically created group.

2) Rename the group scheduler filters that work on the 'affinity' and 'anti-affinity' policies of instance groups.

3) Add new filters with the old names that apply affinity/anti-affinity for instances in groups with the policy of 'scheduler'. They will get applied if you configure the scheduler to use them.

That should result in allow both the new style behavior if you enable the new filters, as well as retain backwards compatibility with the old code / behavior.