Use a tmpdir instead of `git worktree`
Use a tmpdir instead of `git worktree`

There is danger in using a temporary `git worktree` because it git
maintains bookkeeping for each worktree that consumes resources.
Using `git extract` to a tmpdir means that the directory can, in the
most extreme case, be abandoned to the standard temporary directory
cleanup process.

balki-server/myprecious