Re: [PATCH] checkout: do not switch branch during a rebase unless -f is given

> Another approach is to let checkout work as usual, but refuse update refs:
> 
>  - after rebase starts, HEAD can only be updated either by rebase, or
> any commands that keep HEAD a headless ref.
>  - the branch being rebased is locked. No commands but rebase can update it.
> 
> I think the second point is good for all interactive commands like
> rebase. Create a .lock file with a signature inside (e.g. command
> name). If update_ref() callers do not give correct signature, refuse
> to update.