Does not work if run from a worktree

[Timmmm]

If you make a git repository at /foo and then make a worktree at /bar then run autorebase in /bar it fails with a message like this:

• Creating worktree...
Error: process exited with exit code exit code: 128
Command: ["git", "worktree", "add", "--detach", "/bar/.git/autorebase/autorebase_worktree"]
Stdout: Preparing worktree (detached HEAD 7866eaea0a)

Stderr: fatal: could not create leading directories of '/bar/.git/autorebase/autorebase_worktree/.git': Not a directory