Merge branch 'nd/worktree-various-heads'

The experimental "multiple worktree" feature gains more safety to
forbid operations on a branch that is checked out or being actively
worked on elsewhere, by noticing that e.g. it is being rebased.

* nd/worktree-various-heads:
  branch: do not rename a branch under bisect or rebase
  worktree.c: check whether branch is bisected in another worktree
  wt-status.c: split bisect detection out of wt_status_get_state()
  worktree.c: check whether branch is rebased in another worktree
  worktree.c: avoid referencing to worktrees[i] multiple times
  wt-status.c: make wt_status_check_rebase() work on any worktree
  wt-status.c: split rebase detection out of wt_status_get_state()
  path.c: refactor and add worktree_git_path()
  worktree.c: mark current worktree
  worktree.c: make find_shared_symref() return struct worktree *
  worktree.c: store "id" instead of "git_dir"
  path.c: add git_common_path() and strbuf_git_common_path()
  dir.c: rename str(n)cmp_icase to fspath(n)cmp

diff --cc builtin/branch.c
Simple merge

diff --cc builtin/checkout.c
Simple merge

diff --cc builtin/worktree.c
Simple merge

diff --cc cache.h
Simple merge

diff --cc dir.c
Simple merge

diff --cc dir.h
index d56d2fb48f68191d54fdfb8c5c104cb87cba1c41,e34d555d537b82392e0372fd0149d9b62ef3ccd0..bfde698c488adcc75b7a294476c622afb6f92b36
--- 1/dir.h
--- 2/dir.h
+++ b/dir.h
@@@ -270,8 -270,9 +270,8 @@@ extern int remove_dir_recursively(struc
  /* tries to remove the path with empty directories along it, ignores ENOENT */
  extern int remove_path(const char *path);
  
- extern int strcmp_icase(const char *a, const char *b);
- extern int strncmp_icase(const char *a, const char *b, size_t count);
+ extern int fspathcmp(const char *a, const char *b);
+ extern int fspathncmp(const char *a, const char *b, size_t count);
 -extern int fnmatch_icase(const char *pattern, const char *string, int flags);
  
  /*
   * The prefix part of pattern must not contains wildcards.

diff --cc fast-import.c
Simple merge

diff --cc path.c
Simple merge

diff --cc sha1_file.c
Simple merge

diff --cc worktree.c
Simple merge

diff --cc wt-status.c
Simple merge