Merge branch 'rs/pop-recent-commit-with-prio-queue'

The pop_most_recent_commit() function can have quite expensive
worst case performance characteristics, which has been optimized by
using prio-queue data structure.

* rs/pop-recent-commit-with-prio-queue:
  commit: use prio_queue_replace() in pop_most_recent_commit()
  prio-queue: add prio_queue_replace()
  commit: convert pop_most_recent_commit() to prio_queue

diff --cc commit.c
Simple merge

diff --cc fetch-pack.c
Simple merge

diff --cc object-name.c
Simple merge

diff --cc t/meson.build
Simple merge

diff --cc walker.c
Simple merge