[PATCH 0/2] limiting followRemoteHEAD being used

From: Jeff King <peff@peff.net>
Date: Mar 18, 2025, 05:39 UTC
Message-ID: <20250318053905.GA2051217@coredump.intra.peff.net>
In-Reply-To: <xmqq1puva3cu.fsf@gitster.g>

On Mon, Mar 17, 2025 at 12:01:21PM -0700, Junio C Hamano wrote:

Show 17 quoted lines

> > So I could see going in two different directions:
> >
> >   1. Only do the HEAD update when we are using the configured refspecs.
> >
> >   2. Do the HEAD update even when we are not fetching its destination,
> >      but do not otherwise trigger ls-refs to discover it (so basically,
> >      not on object-only fetches). This kicks in for more cases, but is
> >      hard to explain.
> >
> > Both are a user-visible divergence from how the feature behaves now (and
> > so I did not want to touch that in my series), but if we are all in
> > agreement, we can fix it on top. I do think option 1 (i.e., what you are
> > suggesting in your email) is how I would have done it if starting from
> > scratch. And the current rules are weird enough and the feature is new
> > enough that I think it is OK to change.
> 
> Yup, I do think #1 is the way to go.

It turned out to be pretty easy to do; the code ends up even shorter. These patches apply on top of jk/fetch-ref-prefix-cleanup.

There is one interesting case we haven't discussed. What should:

  git fetch origin HEAD

do with respect to refs/remotes/origin/HEAD? Right now it does nothing (at least with the v2 protocol). We ask about HEAD, but since we didn't fetch the matching ref, set_head() won't accept it. And after my patches, we would not even try to call set_head() at all (since we are not using the full refspecs).

But it's also something I could see somebody doing to try to update refs/remotes/origin/HEAD. I've left it alone for now, since my series does not change the behavior either way. But it might be something we could do on top (though it gets funny, because with the code as it is now, we'd have to ask for all of refs/heads/ to see the pointed-to branch advertised).

Anyway, here's what I think we should do now. The first one is the change we discussed, and the second is a related optimization I noticed.

  [1/2]: fetch: only respect followRemoteHEAD with configured refspecs
  [2/2]: fetch: don't ask for remote HEAD if followRemoteHEAD is "never"

 Documentation/config/remote.adoc |  3 ++-
 builtin/fetch.c                  | 29 +++++++----------------------
 t/t5505-remote.sh                |  2 +-
 t/t5510-fetch.sh                 | 19 ++++++++++++++++++-
 4 files changed, 28 insertions(+), 25 deletions(-)