Subject: Re: [PATCH 3/6] refs/files: sort reflogs returned by the reflog iterator

From: Patrick Steinhardt <[email-masked]>
Date: Tue, 20 Feb 2024 09:34:55 +0100

On Mon, Feb 19, 2024 at 04:04:16PM -0800, Junio C Hamano wrote:
> Patrick Steinhardt <[email-masked]> writes:
> 
> > We use a directory iterator to return reflogs via the reflog iterator.
> > This iterator returns entries in the same order as readdir(3P) would and
> > will thus yield reflogs with no discernible order.
> >
> > Set the new `DIR_ITERATOR_SORTED` flag that was introduced in the
> > preceding commit so that the order is deterministic. While the effect of
> > this can only been observed in a test tool, a subsequent commit will
> > start to expose this functionality to users via a new `git reflog list`
> > subcommand.
> >
> > Signed-off-by: Patrick Steinhardt <[email-masked]>
> > ---
> >  refs/files-backend.c           | 4 ++--
> >  t/t0600-reffiles-backend.sh    | 4 ++--
> >  t/t1405-main-ref-store.sh      | 2 +-
> >  t/t1406-submodule-ref-store.sh | 2 +-
> >  4 files changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/refs/files-backend.c b/refs/files-backend.c
> > index 75dcc21ecb..2ffc63185f 100644
> > --- a/refs/files-backend.c
> > +++ b/refs/files-backend.c
> > @@ -2193,7 +2193,7 @@ static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
> >  
> >  	strbuf_addf(&sb, "%s/logs", gitdir);
> >  
> > -	diter = dir_iterator_begin(sb.buf, 0);
> > +	diter = dir_iterator_begin(sb.buf, DIR_ITERATOR_SORTED);
> >  	if (!diter) {
> >  		strbuf_release(&sb);
> >  		return empty_ref_iterator_begin();
> > @@ -2202,7 +2202,7 @@ static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
> >  	CALLOC_ARRAY(iter, 1);
> >  	ref_iterator = &iter->base;
> >  
> > -	base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
> > +	base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 1);
> 
> This caught my attention.  Once we apply this patch, the only way
> base_ref_iterator_init() can receive 0 for its last parameter
> (i.e. 'ordered') is via the merge_ref_iterator_begin() call in
> files_reflog_iterator_begin() that passes 0 as 'ordered'.  If we
> force files_reflog_iterator_begin() to ask for an ordered
> merge_ref_iterator, then we will have no unordered ref iterators.
> Am I reading the code right?

Ah, true indeed. The "files" reflog iterator was the only remaining
iterator that wasn't ordered. I'll include an additional patch on top
that drops the `ordered` bit altogether.

Patrick