This is a replacement for some patches from v2 of my 'git rebase
--update-refs' topic [1]. After some feedback from Philip, I've decided to
pull that topic while I rework how I track the refs to rewrite [2]. This
series moves forward with the branch_checked_out() helper that was a bit
more complicated than expected at first glance. This series is a culmination
of the discussion started by Junio at [3].

[1]
https://lore.kernel.org/git/pull.1247.v2.git.1654634569.gitgitgadget@gmail.com
[2]
https://lore.kernel.org/git/34264915-8a37-62db-f954-0b5297639b34@github.com/
[3] https://lore.kernel.org/git/xmqqr140t9am.fsf@gitster.g/

Here is the patch outline:

 1. Add a basic form of branch_checked_out() that only looks at the HEAD of
    each worktree. Since this doesn't look at BISECT_HEAD or REBASE_HEAD,
    the helper isn't linked to any consumer in this patch. A test script is
    added that verifies the current behavior checks that are implemented,
    even if they are not connected yet.
 2. Make branch_checked_out() actually look at BISECT_HEAD and REBASE_HEAD.
    Add tests for those cases, which was previously untested in the Git test
    suite. Use branch_checked_out() in 'git branch -f' to demonstrate this
    helper works as expected.
 3. Use branch_checked_out() in 'git fetch' when checking refs that would be
    updated by the refspec. Add tests for that scenario, too.
 4. Use branch_checked_out() in 'git branch -D' to prevent deleting refs
    from under an existing checkout. The commit message here describes some
    barriers to removing other uses of find_shared_symref() that could be
    good investigations for later.

Thanks, -Stolee

Derrick Stolee (4):
  branch: add branch_checked_out() helper
  branch: check for bisects and rebases
  fetch: use new branch_checked_out() and add tests
  branch: use branch_checked_out() when deleting refs

 branch.c                  | 77 +++++++++++++++++++++++++++++++++----
 branch.h                  |  8 ++++
 builtin/branch.c          |  8 ++--
 builtin/fetch.c           | 25 ++++++------
 t/t2407-worktree-heads.sh | 81 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 173 insertions(+), 26 deletions(-)
 create mode 100755 t/t2407-worktree-heads.sh

base-commit: 2668e3608e47494f2f10ef2b6e69f08a84816bcb

Submitted-As: https://lore.kernel.org/git/pull.1254.git.1654718942.gitgitgadget@gmail.com