Re: [PATCH v3 6/7] merge: ensure we can actually restore pre-merge state

> The great news: the fact that this affects you means you are using
> non-bare clones in your mergeability checks, and being forced with
> every merge to first checkout the appropriate branch, and pay for the
> penalty of updating both the index and the working tree both in that
> checkout and during the merge (and perhaps in doing a hard reset
> afterwards) in your mergeability check, despite the fact that a
> mergeability check really only needs a boolean: "does it merge
> cleanly?".  Doing a full worktree-tied merge like this is really
> expensive, and while the above Git changes may have made it even more
> expensive for you, the real savings comes from switching to a bare
> clone and not writing any working tree files or the index.  That's
> available via running `git merge-tree`; see the documentation for the
> --write-tree option in particular.  GitHub switched over to it last
> year and GitLab should be switching soon (or may have already
> completed it; I haven't checked in a bit).