Merge branch 'jk/prune-with-corrupt-refs' into maint

"git prune" used to largely ignore broken refs when deciding which objects are still being used, which could spread an existing small damage and make it a larger one. * jk/prune-with-corrupt-refs: refs.c: drop curate_packed_refs repack: turn on "ref paranoia" when doing a destructive repack prune: turn on ref_paranoia flag refs: introduce a "ref paranoia" flag t5312: test object deletion code paths in a corrupted repository