builtin/pack-objects.c: remove duplicate hash lookup

In the original code from 08cdfb1 (pack-objects --keep-unreachable,
2007-09-16), we add each object to the packing list with type
`obj->type`, where `obj` comes from `lookup_unknown_object()`. Unless we
had already looked up and parsed the object, this will be `OBJ_NONE`.
That's fine, since oe_set_type() sets the type_valid bit to '0', and we
determine the real type later on.

So the only thing we need from the object lookup is access to the
`flags` field so that we can mark that we've added the object with
`OBJECT_ADDED` to avoid adding it again (we can just pass `OBJ_NONE`
directly instead of grabbing it from the object).

But add_object_entry() already rejects duplicates! This has been the
behavior since 7a979d9 (Thin pack - create packfile with missing
delta base., 2006-02-19), but 08cdfb1 didn't take advantage of it.
Moreover, to do the OBJECT_ADDED check, we have to do a hash lookup in
`obj_hash`.

So we can drop the lookup_unknown_object() call completely, *and* the
OBJECT_ADDED flag, too, since the spot we're touching here is the only
location that checks it.

In the end, we perform the same number of hash lookups, but with the
added bonus that we don't waste memory allocating an OBJ_NONE object (if
we were traversing, we'd need it eventually, but the whole point of this
code path is not to traverse).

Signed-off-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ttaylorr

builtin/pack-objects.c

@@ -3405,13 +3405,9 @@ static void read_object_list_from_stdin(void)
 	}
 }
 
-/* Remember to update object flag allocation in object.h */
-#define OBJECT_ADDED (1u<<20)
-
 static void show_commit(struct commit *commit, void *data)
 {
 	add_object_entry(&commit->object.oid, OBJ_COMMIT, NULL, 0);
-	commit->object.flags |= OBJECT_ADDED;
 
 	if (write_bitmap_index)
 		index_commit_for_bitmap(commit);
@@ -3424,7 +3420,6 @@ static void show_object(struct object *obj, const char *name, void *data)
 {
 	add_preferred_base_object(name);
 	add_object_entry(&obj->oid, obj->type, name, 0);
-	obj->flags |= OBJECT_ADDED;
 
 	if (use_delta_islands) {
 		const char *p;
@@ -3510,11 +3505,7 @@ static int add_object_in_unpacked_pack(const struct object_id *oid,
 				       uint32_t pos,
 				       void *_data)
 {
-	struct object *obj = lookup_unknown_object(the_repository, oid);
-	if (obj->flags & OBJECT_ADDED)
-		return 0;
-	add_object_entry(oid, obj->type, "", 0);
-	obj->flags |= OBJECT_ADDED;
+	add_object_entry(oid, OBJ_NONE, "", 0);
 	return 0;
 }
 

object.h

@@ -75,7 +75,6 @@ struct object_array {
  * builtin/fsck.c:           0--3
  * builtin/gc.c:             0
  * builtin/index-pack.c:                                     2021
- * builtin/pack-objects.c:                                   20
  * builtin/reflog.c:                   10--12
  * builtin/show-branch.c:    0-------------------------------------------26
  * builtin/unpack-objects.c:                                 2021