builtin/repack: avoid "the_hash_algo" in repack_promisor_objects()

In a similar spirit as the previous commits, avoid referring directly to
"the_hash_algo" within builtin/repack.c::repack_promisor_objects().

Since there is already a repository pointer in scope, use its hash_algo
value instead.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: ttaylorr

builtin/repack.c

@@ -452,7 +452,7 @@ static void repack_promisor_objects(struct repository *repo,
 		struct string_list_item *item;
 		char *promisor_name;
 
-		if (line.len != the_hash_algo->hexsz)
+		if (line.len != repo->hash_algo->hexsz)
 			die(_("repack: Expecting full hex object ID lines only from pack-objects."));
 		item = string_list_append(names, line.buf);