From: Phillip Wood <phillip.wood123@gmail.com>
Date: Tue, 28 Jul 2026 09:36:33 GMT
Subject: Re: [PATCH v3 1/2] rebase: skip branch symref aliases
Message-ID: <8631114b-aa6f-446e-9710-92c400320eac@gmail.com>
In-Reply-To: <xmqq7bmhycxq.fsf@gitster.g>

On 26/07/2026 16:42, Junio C Hamano wrote:
> Phillip Wood <phillip.wood123@gmail.com> writes:
> 
>>> Thanks for re-rolling I'm pretty sure the logic is sound now but I'm a
>>> bit confused by a couple of things - see my comments below.
>>> ...
>>> It would be nice to have a comment here explaining what we're doing.
>>> Also I don't think we need to copy the refname so it would be more
>>> efficient to use refs_resolve_ref_unsafe().
>>
>> Looking at this again we cannot use refs_resolve_ref_unsafe() because
>> the result would be overwritten by the call to refs_resolve_refdup() in
>> branch_checked_out().
> 
> Makes sense.  Thanks for raising a possible alternative and then
> clarifying that it is not quite workable.
> 
>>>> +        /*
>>>> +         * If the branch is the current HEAD, then it will be
>>>> +         * updated by the default rebase behavior.
>>>> +         */
>>>> +        if (head_ref && !strcmp(head_ref, decoration->name)) {
>>>> +            free(resolved_ref);
>>>>                decoration = decoration->next;
>>>>                continue;
>>>>            }
>>>
>>> Then we check to see if the decoration matches HEAD which we used to do
>>> above - I'm not clear why we have moved this check.
>>
>> Should we be using "resolved_ref" instead of "decoration->name"? That
>> would explain why this was moved and would makes sense as we resolve
>> symrefs when reading HEAD. When HEAD points outside "refs/heads/" we'd
>> then skip updating any symrefs under "refs/heads/" that pointed to the
>> same ref as HEAD.
> 
> Yeah, decoration is very much end-user facing and if we can make
> behavioural decision based on a more stable resolved_ref that would
> make it easier to reason about.
> 
> But stepping back a bit, is having a HEAD that is a symref and
> points outside "refs/heads/" an invalid state?  Why are we catering
> to such a configuration to begin with?

We allow HEAD to point to anything below "refs/" - see e9cc02f0e4 
(symbolic-ref: allow refs/<whatever> in HEAD, 2009-02-13). I've not 
tested it but looking at the code I think rebase handles a non-branch 
HEAD correctly.

It would be nice if we didn't have to worry about non-branch HEADs, 
recently Caleb reported on discord being surprised that git allows HEAD 
to point to a tag.

Thanks

Phillip