RE: [PATCH 0/4] [RFC] merge --autostash: apply autostash in more cases

> This series aims to apply the stash created by 'git merge --autostash' in 2
> situations that were not covered by the code:
> 
>  1. If the merge is fast-forward but the fast-forward operation fails -
>     PATCH 3/4
>  2. If the merge strategy completely fails to handle the merge (exit code 2)
>     - PATCH 4/4
> 
> The first 2 commits are small improvements that I noticed while implementing
> the other two.
> 
> I'm marking it [RFC] because I'm not 100% sure that trying to apply the
> autostash in 3/4 and 4/4 is actually the best course of action (or if it
> would be better to call 'save_autostash' instead). That's because:
> 
> For 3/4 (fast-forward fails): I'm not sure if 'unpack_trees' (called by
> 'checkout_fast_forward') is guaranteed to fail atomically, or it might fail
> mid-way and leave the worktree unclean, in which case it might be better not
> to apply the autostash, but just save it instead (and tell the user). In the
> test case I'm adding, it does fail before starting to update the working
> tree, but I'm not sure if it's always the case.