Re: [PATCH 1/5] describe: pass oid struct by const pointer

> We pass a "struct object_id" to describe_blob() by value. This isn't
> wrong, as an oid is composed only of copy-able values. But it's unusual;
> typically we pass structs by const pointer, including object_ids. Let's
> do so.
>
> It similarly makes sense for us to hold that pointer in the callback
> data (rather than yet another copy of the oid).
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> Not strictly related, but I noticed while in the area and remembered a
> recent discussion in this direction.

>  builtin/describe.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/builtin/describe.c b/builtin/describe.c
> index d7dd8139de..383d3e6b9a 100644
> --- a/builtin/describe.c
> +++ b/builtin/describe.c
> @@ -490,7 +490,7 @@ static void describe_commit(struct object_id *oid, struct strbuf *dst)
>  
>  struct process_commit_data {
>  	struct object_id current_commit;
> -	struct object_id looking_for;
> +	const struct object_id *looking_for;
>  	struct strbuf *dst;
>  	struct rev_info *revs;
>  };
> @@ -505,7 +505,7 @@ static void process_object(struct object *obj, const char *path, void *data)
>  {
>  	struct process_commit_data *pcd = data;
>  
> -	if (oideq(&pcd->looking_for, &obj->oid) && !pcd->dst->len) {
> +	if (oideq(pcd->looking_for, &obj->oid) && !pcd->dst->len) {
>  		reset_revision_walk();
>  		describe_commit(&pcd->current_commit, pcd->dst);
>  		strbuf_addf(pcd->dst, ":%s", path);
> @@ -514,7 +514,7 @@ static void process_object(struct object *obj, const char *path, void *data)
>  	}
>  }
>  
> -static void describe_blob(struct object_id oid, struct strbuf *dst)
> +static void describe_blob(const struct object_id *oid, struct strbuf *dst)
>  {
>  	struct rev_info revs;
>  	struct strvec args = STRVEC_INIT;
> @@ -554,7 +554,7 @@ static void describe(const char *arg, int last_one)
>  		describe_commit(&oid, &sb);
>  	else if (odb_read_object_info(the_repository->objects,
>  				      &oid, NULL) == OBJ_BLOB)
> -		describe_blob(oid, &sb);
> +		describe_blob(&oid, &sb);
>  	else
>  		die(_("%s is neither a commit nor blob"), arg);