Subject: Re: [PATCH 11/11] bundle: unbundle promisor packs

From: Junio C Hamano <[email-masked]>
Date: Fri, 04 Mar 2022 15:43:33 -0800

"Derrick Stolee via GitGitGadget" <[email-masked]> writes:

> From: Derrick Stolee <[email-masked]>
>
> In order to have a valid pack-file after unbundling a bundle that has
> the 'filter' capability, we need to generate a .promisor file. The
> bundle does not promise _where_ the objects can be found, but we can
> expect that these bundles will be unbundled in repositories with
> appropriate promisor remotes that can find those missing objects.

That sounds like a lot of wishful thinking, but I do not think of a
better way to phrase the idea.  Taking a bundle out of a repository
and unbundling it elsewhere is "git fetch" that could be done to
send objects from the former to the latter repository, so I am OK
with the assumption that the original repository will stay available
for such users who took its contents over sneaker-net instead of
over the wire.

> Use the 'git index-pack --promisor=<message>' option to create this
> .promisor file. Add "from-bundle" as the message to help anyone diagnose
> issues with these promisor packs.
>
> Signed-off-by: Derrick Stolee <[email-masked]>
> ---
>  bundle.c               | 4 ++++
>  t/t6020-bundle-misc.sh | 8 +++++++-
>  2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/bundle.c b/bundle.c
> index e284ef63062..3d97de40ef0 100644
> --- a/bundle.c
> +++ b/bundle.c
> @@ -631,6 +631,10 @@ int unbundle(struct repository *r, struct bundle_header *header,
>  	struct child_process ip = CHILD_PROCESS_INIT;
>  	strvec_pushl(&ip.args, "index-pack", "--fix-thin", "--stdin", NULL);
>  
> +	/* If there is a filter, then we need to create the promisor pack. */
> +	if (header->filter)
> +		strvec_push(&ip.args, "--promisor=from-bundle");
> +
>  	if (extra_index_pack_args) {
>  		strvec_pushv(&ip.args, extra_index_pack_args->v);
>  		strvec_clear(extra_index_pack_args);
> diff --git a/t/t6020-bundle-misc.sh b/t/t6020-bundle-misc.sh
> index 39cfefafb65..344af34db1e 100755
> --- a/t/t6020-bundle-misc.sh
> +++ b/t/t6020-bundle-misc.sh
> @@ -513,7 +513,13 @@ do
>  		The bundle uses this filter: $filter
>  		The bundle records a complete history.
>  		EOF
> -		test_cmp expect actual
> +		test_cmp expect actual &&
> +
> +		# This creates the first pack-file in the
> +		# .git/objects/pack directory. Look for a .promisor.
> +		git bundle unbundle partial.bdl &&
> +		ls .git/objects/pack/pack-*.promisor >promisor &&
> +		test_line_count = 1 promisor

OK.  Do we also want to inspect the contents of the resulting
repository to make sure that the bundle had the right contents?

One idea to do so would probably be

 - prepare a test repository (you already have it)
 - prepare a partial.bdl (you already do this)

 - clone the test repository into a new repository, with the same
   filter
 - create an empty repository, unbundle the partial.bdl

 - take "for-each-ref" and list of objects available in these two
   "partial copies" from the test repository, and compare