Re: [PATCH] ref-filter: don't look for objects when outside of a repository

[Junio C Hamano <gitster@pobox.com>]

SZEDER Gábor <szeder.dev@gmail.com> writes:

> The command 'git ls-remote --sort=authordate <remote>' segfaults when
> run outside of a repository, ever since the introduction of its
> '--sort' option in 1fb20dfd8e (ls-remote: create '--sort' option,
> 2018-04-09).
>
> While in general the 'git ls-remote' command can be run outside of a
> repository just fine, its '--sort=<key>' option with certain keys does
> require access to the referenced objects.  This sorting is implemented
> using the generic ref-filter sorting facility, which already handles
> missing objects gracefully with the appropriate 'missing object
> deadbeef for HEAD' message.  However, being generic means that it
> checks replace refs while trying to retrieve an object, and while
> doing so it accesses the 'git_replace_ref_base' variable, which has
> not been initialized and is still a NULL pointer when outside of a
> repository, thus causing the segfault.
>
> Make ref-filter more careful and only attempt to retrieve an object
> when we are in a repository.  Also add a test to ensure that 'git
> ls-remote --sort' fails gracefully when executed outside of a
> repository.

OK.  So by forcing get_object() return an error, we do the same to
populate_value() which in turn will make get_ref_atgom_value return
an error and cmp_ref_sorting() will notice and die.

I think that is the best we could do.

>
> Reported-by: H.Merijn Brand <h.m.brand@xs4all.nl>
> Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
> ---
>
> I'm not quite sure that this is the best place to add this check...
> but hey, it's a Saturday afternoon after all ;)
>
>  ref-filter.c         | 3 ++-
>  t/t5512-ls-remote.sh | 6 ++++++
>  2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/ref-filter.c b/ref-filter.c
> index e1bcb4ca8a..3555bc29e7 100644
> --- a/ref-filter.c
> +++ b/ref-filter.c
> @@ -1473,7 +1473,8 @@ static int get_object(struct ref_array_item *ref, int deref, struct object **obj
>  		oi->info.sizep = &oi->size;
>  		oi->info.typep = &oi->type;
>  	}
> -	if (oid_object_info_extended(the_repository, &oi->oid, &oi->info,
> +	if (!have_git_dir() ||
> +	    oid_object_info_extended(the_repository, &oi->oid, &oi->info,
>  				     OBJECT_INFO_LOOKUP_REPLACE))
>  		return strbuf_addf_ret(err, -1, _("missing object %s for %s"),
>  				       oid_to_hex(&oi->oid), ref->refname);
> diff --git a/t/t5512-ls-remote.sh b/t/t5512-ls-remote.sh
> index bc5703ff9b..7dd081da01 100755
> --- a/t/t5512-ls-remote.sh
> +++ b/t/t5512-ls-remote.sh
> @@ -302,4 +302,10 @@ test_expect_success 'ls-remote works outside repository' '
>  	nongit git ls-remote dst.git
>  '
>  
> +test_expect_success 'ls-remote --sort fails gracefully outside repository' '
> +	# Use a sort key that requires access to the referenced objects.
> +	nongit test_must_fail git ls-remote --sort=authordate "$TRASH_DIRECTORY" 2>err &&
> +	test_i18ngrep "^fatal: missing object" err
> +'
> +
>  test_done