Merge branch 'ja/worktree-orphan'

'git worktree add' learned how to create a worktree based on an
orphaned branch with `--orphan`.

* ja/worktree-orphan:
  worktree add: emit warn when there is a bad HEAD
  worktree add: extend DWIM to infer --orphan
  worktree add: introduce "try --orphan" hint
  worktree add: add --orphan flag
  t2400: add tests to verify --quiet
  t2400: refactor "worktree add" opt exclusion tests
  t2400: cleanup created worktree in test
  worktree add: include -B in usage docs

diff --cc builtin/worktree.c
index 60e389aaedb20e6d13cf2233902fe32ec3f7ae20,5f620843341a9cc26d0c99f35080ad2bd2b68e41..2931cd0230a4bbc0179f0a8093b1e535c3a99c57
--- 1/builtin/worktree.c
--- 2/builtin/worktree.c
+++ b/builtin/worktree.c
@@@ -1,8 -1,8 +1,9 @@@
  #include "cache.h"
  #include "abspath.h"
+ #include "advice.h"
  #include "checkout.h"
  #include "config.h"
 +#include "copy.h"
  #include "builtin.h"
  #include "dir.h"
  #include "environment.h"
@@@ -14,7 -12,7 +15,8 @@@
  #include "strvec.h"
  #include "branch.h"
  #include "refs.h"
+ #include "remote.h"
 +#include "repository.h"
  #include "run-command.h"
  #include "hook.h"
  #include "sigchain.h"