Re: [PATCH 2/3] t1405: mark test that checks existence as REFFILES

[Han-Wen Nienhuys <hanwen@google.com>]

On Mon, Feb 7, 2022 at 10:48 AM Han-Wen Nienhuys <hanwen@google.com> wrote:
>
> On Fri, Feb 4, 2022 at 12:06 AM Junio C Hamano <gitster@pobox.com> wrote:
> >
> > Han-Wen Nienhuys <hanwen@google.com> writes:
> >
> > > Technically, the only obstacle I see is that we'd need to treat an
> > > existence entry especially for the purpose of compaction/gc: we can
> > > discard older entries, but we shouldn't discard the existence bit, no
> > > matter how old it is.
> >
> > I was hoping that we already have a type of block that can be used
> > to record an attribute on the ref (other than its value) and it
> > would be just the matter of stealing one unused bit from such a
> > record per ref to say "when answering 'does this ref have reflog?'
> > say yes even when there is no log record for that refname".  Or the
> > table format is extensible enough that we can add such a block
> > without breaking existing clients.
>
> That place doesn't exist, unfortunately, but even if it did, having a
> special reflog entry indicating existence is a better solution all
> around, I think. A separate per-ref bit allows for data
> inconsistencies: what if the bit says "there is no reflog", but we
> actually do have reflog entries in the 'g' section?
>
> It also has less chances of creating complicated control flows
> (especially in JGit which wasn't designed for this bit from the
> start): the tables have to be written in lexicographic order, so you
> only can write this bit after you know if reflog entries were written
> for a certain ref.

Correction. I wish the table blocks were written in lexicographic
order, but they are written in order 'g', ['i',] 'o', ['i'], 'g',
['i']. Since the 'g' block is last within a table, we could add a new
section at the end.  My point that this is considerable work to think
through how to make this work with JGit still stands, though.

-- 
Han-Wen Nienhuys - Google Munich
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