Merge branch 'kk/streaming-walk-pqueue'

Streaming revision walks have been optimized by using a priority queue for date-sorting commits, speeding up walks repositories with many merges. * kk/streaming-walk-pqueue: revision: use priority queue for non-limited streaming walks revision: introduce rev_walk_mode to clarify get_revision_1() pack-objects: call release_revisions() after cruft traversal