Merge branch 'ns/tmp-objdir' into en/remerge-diff

* ns/tmp-objdir:
  tmp-objdir: disable ref updates when replacing the primary odb
  tmp-objdir: new API for creating temporary writable databases

diff --cc builtin/prune.c
Simple merge

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

diff --cc environment.c
Simple merge

diff --cc object-file.c
Simple merge

diff --cc object-store.h
Simple merge

diff --cc object.c
Simple merge

diff --cc refs.c
Simple merge

diff --cc repository.c
Simple merge

diff --cc repository.h
Simple merge