Re: [PATCH v3 0/3] Remove special casing for PSEUDOREF updates

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 5, 2020, 15:54 UTC
Message-ID: <xmqqk0ydozqe.fsf@gitster.c.googlers.com>
In-Reply-To: <CAFQ2z_NU4=WcUDvVY9PNs+p-WU4u5=QY+=DHonGyK29numhWoQ@mail.gmail.com>

Han-Wen Nienhuys <hanwen@google.com> writes:

Show 7 quoted lines

>> All of which means FETCH_HEAD is special and we may not want to
>> burden the special casing of it to newer backends.
>
> Can you confirm that FETCH_HEAD is the only thing that can store more
> than just a symref / SHA1 ? Based on the name, and a comment in the
> JGit source, I thought that MERGE_HEAD might contain more than one
> SHA1 at a time.

No I cannot. I do not think MERGE_HEAD is something I added with as deep a thought as I did with FETCH_HEAD. If it mimics FETCH_HEAD, then perhaps it does, but I somehow doubt it.

As can be seen in builtin/merge.c::collect_parents(), we do special case FETCH_HEAD when grabbing what commit*S* to merge, but all others are read with get_merge_parent() that makes a single call to get_oid(), i.e. anything other than FETCH_HEAD cannot have more than one object recorded.