Subject: Re: [PATCH 11/12] receive-pack: treat namespace .have lines like alternates

From: Junio C Hamano <[email-masked]>
Date: Wed, 25 Jan 2017 11:51:17 -0800

Jeff King <[email-masked]> writes:

> Namely, de-duplicate them. We use the same set as the
> alternates, since we call them both ".have" (i.e., there is
> no value in showing one versus the other).
>
> Signed-off-by: Jeff King <[email-masked]>
> ---
>  builtin/receive-pack.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
> index 8f8762e4a..c55e2f993 100644
> --- a/builtin/receive-pack.c
> +++ b/builtin/receive-pack.c
> @@ -251,8 +251,9 @@ static void show_ref(const char *path, const unsigned char *sha1)
>  }
>  
>  static int show_ref_cb(const char *path_full, const struct object_id *oid,
> -		       int flag, void *unused)
> +		       int flag, void *data)
>  {
> +	struct oidset *seen = data;
>  	const char *path = strip_namespace(path_full);
>  
>  	if (ref_is_hidden(path, path_full))
> @@ -263,8 +264,11 @@ static int show_ref_cb(const char *path_full, const struct object_id *oid,
>  	 * refs, so that the client can use them to minimize data
>  	 * transfer but will otherwise ignore them.
>  	 */
> -	if (!path)
> +	if (!path) {
> +		if (oidset_insert(seen, oid))
> +			return 0;
>  		path = ".have";
> +	}

This is very sensible as an optimization that does not change
semantics.

This is an unrelated tangent, but there may want to be a knob to
make the code return here without even showing, to make the
advertisement even smaller and also to stop miniscule information
leakage?  If the namespaced multiple projects are totally unrelated
(i.e. "My sysadmin gave me a write access only to this single
directory, so I am using the namespace feature to host these three
projects that have nothing to do with each other"), showing objects
of other namespaces will buy us nothing and the user is better off
without this code showing these refs as ".have".

>  	show_ref(path, oid->hash);
>  	return 0;
>  }
> @@ -287,7 +291,7 @@ static void write_head_info(void)
>  
>  	for_each_alternate_ref(show_one_alternate_ref, &seen);
>  	oidset_clear(&seen);
> -	for_each_ref(show_ref_cb, NULL);
> +	for_each_ref(show_ref_cb, &seen);
>  	if (!sent_capabilities)
>  		show_ref("capabilities^{}", null_sha1);