From: Elijah Newren <newren@gmail.com>
Date: Fri, 01 Oct 2021 03:59:46 GMT
Subject: Re: [PATCH 5/7] tmp-objdir: new API for creating and removing primary object dirs
Message-ID: <CABPp-BGgytcH5kBF_xuukz=FfEi0-076AsvCsW=1otycAOMbdQ@mail.gmail.com>
In-Reply-To: <xmqqbl49bzfy.fsf@gitster.g>

On Thu, Sep 30, 2021 at 1:06 PM Junio C Hamano <gitster@pobox.com> wrote:
>
> Jeff King <peff@peff.net> writes:
>
> >   - is it possible for the merge code to ever write an object? I kind of
> >     wonder if we'd ever do any cache-able transformations as part of a
> >     content-level merge. I don't think we do now, though.
>
> How is virtual merge base, result of an inner merge that recursively
> merging two merge bases, fed to an outer merge as the ancestor?
> Isn't it written as a tree object by the inner merge as a tree with
> full of blob objects, so the outer merge does not have to treat a
> merge base tree that is virtual any specially from a sole merge
> base?

Yes.  And that's not unique to the inner merges; it also writes new
blob and tree objects for the outer merge, and then passes the
resulting toplevel tree id out as the result.