Merge branch 'tb/pack-bitmap'

Merge branch 'tb/pack-bitmap'

Various improvements to the codepath that writes out pack bitmaps.

* tb/pack-bitmap: (24 commits)
  pack-bitmap-write: better reuse bitmaps
  pack-bitmap-write: relax unique revwalk condition
  pack-bitmap-write: use existing bitmaps
  pack-bitmap: factor out 'add_commit_to_bitmap()'
  pack-bitmap: factor out 'bitmap_for_commit()'
  pack-bitmap-write: ignore BITMAP_FLAG_REUSE
  pack-bitmap-write: build fewer intermediate bitmaps
  pack-bitmap.c: check reads more aggressively when loading
  pack-bitmap-write: rename children to reverse_edges
  t5310: add branch-based checks
  commit: implement commit_list_contains()
  bitmap: implement bitmap_is_subset()
  pack-bitmap-write: fill bitmap with commit history
  pack-bitmap-write: pass ownership of intermediate bitmaps
  pack-bitmap-write: reimplement bitmap writing
  ewah: add bitmap_dup() function
  ewah: implement bitmap_or()
  ewah: make bitmap growth less aggressive
  ewah: factor out bitmap growth
  rev-list: die when --test-bitmap detects a mismatch
  ...