make mq play nicely with the branch cache
- if no patches are applied, don't do anything different
- if the cache includes valid data from one of the patch revisions,
use the cache, but don't save anything new
- if the cache has data from before the patch revisions only,
save what the list of branches would be without the patch revisions
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)