Merge branch 'lm/add-p-context' into next

"git add/etc -p" now honors diff.context configuration variable,
and learns to honor -U<n> option.

* lm/add-p-context:
  add-patch: add diff.context command line overrides
  add-patch: respect diff.context configuration
  t: use test_config in t4055
  t: use test_grep in t3701 and t4055

diff --cc Documentation/git-restore.adoc
Simple merge

diff --cc Documentation/git-stash.adoc
Simple merge

diff --cc builtin/add.c
Simple merge

diff --cc builtin/checkout.c
Simple merge

diff --cc builtin/commit.c
Simple merge

diff --cc builtin/reset.c
Simple merge

diff --cc builtin/stash.c
Simple merge

diff --cc commit.h
Simple merge

diff --cc parse-options.h
Simple merge