Merge branch 'ks/pack-objects-bitmap'

Some codepaths in "git pack-objects" were not ready to use an
existing pack bitmap; now they are and as the result they have
become faster.

* ks/pack-objects-bitmap:
pack-objects: use reachability bitmap index when generating non-stdout pack
pack-objects: respect --local/--honor-pack-keep/--incremental when bitmap is in use

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

diff --cc t/t5310-pack-bitmaps.sh
Simple merge