Merge branch 'jt/remove-pack-bitmap-global'

The effort to move globals to per-repository in-core structure
continues.

* jt/remove-pack-bitmap-global:
pack-bitmap: add free function
pack-bitmap: remove bitmap_git global variable

diff --cc builtin/pack-objects.c
Simple merge

diff --cc builtin/rev-list.c
Simple merge

diff --cc pack-bitmap-write.c
Simple merge