Refactor this so that we check the cached packfile at the beginning. We
don't have to re-verify whether the packfile meets the properties as we
have already verified those when storing the pack in `last_found` in the
first place. So all we need to do is to use `find_pack_entry_one()` to
check whether the pack contains the object ID, and to skip the cached
pack in the loop so that we don't search it twice.

This refactoring significantly simplifies the logic and makes it much
easier to follow.

Signed-off-by: Patrick Steinhardt <redacted>
---
 builtin/pack-objects.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 5348aebbe9f..861fef3f38a 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c

@@ -4388,27 +4388,27 @@ static void add_unreachable_loose_objects(struct rev_info *revs)
 
 static int has_sha1_pack_kept_or_nonlocal(const struct object_id *oid)
 {
-	struct packfile_store *packs = the_repository->objects->packfiles;
 	static struct packed_git *last_found = (void *)1;
 	struct packed_git *p;
 
-	p = (last_found != (void *)1) ? last_found :
-					packfile_store_get_packs(packs);
+	if (last_found != (void *)1 && find_pack_entry_one(oid, last_found))
+		return 1;
 
-	while (p) {
-		if ((!p->pack_local || p->pack_keep ||
-				p->pack_keep_in_core) &&
-			find_pack_entry_one(oid, p)) {
+	repo_for_each_pack(the_repository, p) {
+		if ((!p->pack_local || p->pack_keep || p->pack_keep_in_core) &&
+		    find_pack_entry_one(oid, p)) {
 			last_found = p;
 			return 1;
 		}
-		if (p == last_found)
-			p = packfile_store_get_packs(packs);
-		else
-			p = p->next;
-		if (p == last_found)
-			p = p->next;
+
+		/*
+		 * We have already checked `last_found`, so there is no need to
+		 * re-check here.
+		 */