Merge branch 'td/ref-filter-memoize-contains'

'git branch --contains' and 'git for-each-ref --contains' have been
optimized to use the memoized commit traversal previously used only by
'git tag --contains', significantly speeding up connectivity checks
across many candidate refs with shared history.

* td/ref-filter-memoize-contains:
  commit-reach: die on contains walk errors
  ref-filter: memoize --contains with generations
  commit-reach: reject cycles in contains walk

diff --cc commit-reach.c
Simple merge

diff --cc t/t7004-tag.sh
Simple merge