Merge branch 'jk/repack-keep-unreachable'

"git repack" learned the "--keep-unreachable" option, which sends loose unreachable objects to a pack instead of leaving them loose. This helps heuristics based on the number of loose objects (e.g. "gc --auto"). * jk/repack-keep-unreachable: repack: extend --keep-unreachable to loose objects repack: add --keep-unreachable option repack: document --unpack-unreachable option