Re: [PATCH 4/5] describe: handle blob traversal with no commits

From: Jeff King <peff@peff.net>
Date: Aug 19, 2025, 16:59 UTC
Message-ID: <20250819165947.GA1050577@coredump.intra.peff.net>
In-Reply-To: <aKQwP01nulsquhzi@pks.im>

On Tue, Aug 19, 2025 at 10:05:19AM +0200, Patrick Steinhardt wrote:

Show 17 quoted lines

> > I didn't include a test here because it requires corrupting the
> > repository in a way that is only easy to do using the files ref backend.
> > It doesn't seem worth carrying a REFFILES test just for this oddity.
> 
> True:
> 
>     $ git update-ref HEAD HEAD^{tree}
>     fatal: update_ref failed for ref 'HEAD': trying to write non-commit object 4b825dc642cb6eb9a060e54bf8d69288fbee4904 to branch 'HEAD'
> 
> But:
> 
>     $ git update-ref refs/some/tree HEAD^{tree}
>     $ git symbolic-ref HEAD refs/some/tree
>     $ git show
>     tree HEAD
> 
> So that should allow you to write a test, right?

Hrm, that seems like a bug. I thought we insisted that HEAD point at refs/heads.

Ah, no. We did that in b229d18a80 (validate_headref: tighten ref-matching to just branches, 2009-01-29), but had to revert it in e9cc02f0e4 (symbolic-ref: allow refs/<whatever> in HEAD, 2009-02-13) to keep compatibility for topgit. :(

Still, I'm not sure it's something I'd want to base a test on. Maybe if there is a big comment that says "It is OK to invalidate and remove this test if we ever tighten symbolic-ref" it would be OK?

-Peff