From: Kristofer Karlsson <krka@spotify.com>
Date: Tue, 03 Nov 2026 08:35:07 GMT
Subject: Re: [PATCH] rev-list: ignore replacements in the connectivity check
Message-ID: <CAL71e4M7yFnTzYD0eVVGRmzkzSXbU0KZ-JScQOyB4-dB5xkAHA@mail.gmail.com>
In-Reply-To: <xmqq4idyhotf.fsf@gitster.g>

On Mon, 2 Nov 2026 at 23:05, Junio C Hamano <gitster@pobox.com> wrote:
>
> "Kristofer Karlsson via GitGitGadget" <gitgitgadget@gmail.com>
> writes:
>
> > Teach the connectivity check to ignore replacements as well, so
> > that it verifies the same objects that the commands relying on its
> > result will read.
>
> Sounds like absolutely the right thing to do.  We might want to say
> that we check both the original and the replacement, i.e., instead
> of ignoring replace refs, we ensure that the commits, trees, and
> blobs reachable from the replacement objects all exist by treating
> those objects as if they were also at the tips of the connectivity
> graph.
>
> [snip]
> We can address the "shouldn't we make sure that replacement objects
> used when the resulting history is in use are backed by objects
> reachable from them?" issue separately.

I have not fully thought this through yet, but I'm happy
to follow up with further strengthening if there's a gap here.

My preliminary thinking is that since replacements are
implemented as regular refs (refs/replace/OLD -> NEW),
their reachable objects should already be covered by
ordinary connectivity checks when those refs are fetched
or pushed.

And thanks for the review!
Kristofer