Subject: Re: [PATCH 07/11] bundle: safely handle --objects option

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Mon, 07 Mar 2022 16:35:25 +0100

On Wed, Feb 23 2022, Derrick Stolee via GitGitGadget wrote:

> From: Derrick Stolee <[email-masked]>
>
> Since 'git bundle' uses setup_revisions() to specify the object walk,
> some options do not make sense to include during the pack-objects child
> process. Further, these options are used for a call to
> traverse_commit_list() which would then require a callback which is
> currently NULL.
>
> By populating the callback we prevent a segfault in the case of adding
> the --objects flag. This is really a redundant statement because the
> bundles are constructing a pack-file containing all objects in the
> discovered commit range.
>
> Adding --objects to a 'git bundle' command might cause a slower command,
> but at least it will not have a hard failure when the user supplies this
> option. We can also disable walking trees and blobs in advance of this
> walk.
>
> Signed-off-by: Derrick Stolee <[email-masked]>
> ---
>  bundle.c               | 10 +++++++++-
>  t/t6020-bundle-misc.sh | 12 ++++++++++++
>  2 files changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/bundle.c b/bundle.c
> index a0bb687b0f4..dc56db9a50a 100644
> --- a/bundle.c
> +++ b/bundle.c
> @@ -451,6 +451,12 @@ struct bundle_prerequisites_info {
>  	int fd;
>  };
>  
> +
> +static void ignore_object(struct object *obj, const char *v, void *data)
> +{
> +	/* Do nothing. */
> +}
> +
>  static void write_bundle_prerequisites(struct commit *commit, void *data)
>  {
>  	struct bundle_prerequisites_info *bpi = data;
> @@ -544,7 +550,9 @@ int create_bundle(struct repository *r, const char *path,
>  		die("revision walk setup failed");
>  	bpi.fd = bundle_fd;
>  	bpi.pending = &revs_copy.pending;
> -	traverse_commit_list(&revs, write_bundle_prerequisites, NULL, &bpi);
> +
> +	revs.blob_objects = revs.tree_objects = 0;
> +	traverse_commit_list(&revs, write_bundle_prerequisites, ignore_object, &bpi);
>  	object_array_remove_duplicates(&revs_copy.pending);

The callback dummy callback part of it seems like something we'd be
better off doing by just teaching traverse_commit_list() to pay
attention to our "NULL" in this case.

But maybe I'd don't quite get why it either can't say "oh it's, NULL,
don't need to call that", or alternatively die earlier as it notices it
needs to call it, but it wasn't provided.

The same presumably goes for show_commit_fn.