Merge branch 'jc/maint-1.6.0-keep-pack' into maint-1.6.1

* jc/maint-1.6.0-keep-pack: pack-objects: don't loosen objects available in alternate or kept packs t7700: demonstrate repack flaw which may loosen objects unnecessarily Remove --kept-pack-only option and associated infrastructure pack-objects: only repack or loosen objects residing in "local" packs git-repack.sh: don't use --kept-pack-only option to pack-objects t7700-repack: add two new tests demonstrating repacking flaws is_kept_pack(): final clean-up Simplify is_kept_pack() Consolidate ignore_packed logic more has_sha1_kept_pack(): take "struct rev_info" has_sha1_pack(): refactor "pretend these packs do not exist" interface git-repack: resist stray environment variable