Merge branch 'ds/disable-replace-refs'

Introduce a mechanism to disable replace refs globally and per
repository.

* ds/disable-replace-refs:
  repository: create read_replace_refs setting
  replace-objects: create wrapper around setting
  repository: create disable_replace_refs()

diff --cc builtin/fsck.c
Simple merge

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

diff --cc commit-graph.c
Simple merge

diff --cc config.c
Simple merge

diff --cc environment.c
Simple merge

diff --cc git.c
Simple merge

diff --cc log-tree.c
Simple merge

diff --cc repository.h
Simple merge