Merge branch 'hn/checkout-m-autostash-refine' into jch

The autostash fallback in 'git checkout -m' has been refined to only
retry when there are local changes.  Additionally, a blank line now
visually separates autostash conflict advice from the subsequent
branch-switch message.

* hn/checkout-m-autostash-refine:
  checkout -m: refine autostash fallback
  sequencer: teach autostash apply to report conflicts

diff --cc builtin/checkout.c
Simple merge

diff --cc builtin/merge.c
Simple merge

diff --cc sequencer.c
Simple merge

diff --cc sequencer.h
Simple merge

diff --cc t/t7201-co.sh
Simple merge