"git for-each-ref" and friends that list refs used to allow only
one --merged or --no-merged to filter them; they learned to take
combination of both kind of filtering.
* al/ref-filter-merged-and-no-merged:
Doc: prefer more specific file name
ref-filter: make internal reachable-filter API more precise
ref-filter: allow merged and no-merged filters
Doc: cover multiple contains/no-contains filters
t3201: test multiple branch filter combinations