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

"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

diff --cc Documentation/git.txt
Simple merge

diff --cc builtin/repack.c
Simple merge

diff --cc cache.h
Simple merge

diff --cc refs.c
Simple merge