for_each_object_in_pack(): clarify pack vs index ordering

We may return objects in one of two orders: how they appear in the .idx
(sorted by object id) or how they appear in the packfile itself. To
further complicate matters, we have two ordering variables, "i" and
"pos", and it is not clear to which order they apply.

Let's clarify this by using an unambiguous name where possible, and
leaving a comment for the variable that does double-duty.

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

Author: peff

packfile.c

@@ -2082,19 +2082,31 @@ int for_each_object_in_pack(struct packed_git *p,
 	}
 
 	for (i = 0; i < p->num_objects; i++) {
-		uint32_t pos;
+		uint32_t index_pos;
 		struct object_id oid;
 
+		/*
+		 * We are iterating "i" from 0 up to num_objects, but its
+		 * meaning may be different, depending on the requested output
+		 * order:
+		 *
+		 *   - in object-name order, it is the same as the index order
+		 *     used by nth_packed_object_id(), so we can pass it
+		 *     directly
+		 *
+		 *   - in pack-order, it is pack position, which we must
+		 *     convert to an index position in order to get the oid.
+		 */
 		if (flags & FOR_EACH_OBJECT_PACK_ORDER)
-			pos = pack_pos_to_index(p, i);
+			index_pos = pack_pos_to_index(p, i);
 		else
-			pos = i;
+			index_pos = i;
 
-		if (nth_packed_object_id(&oid, p, pos) < 0)
+		if (nth_packed_object_id(&oid, p, index_pos) < 0)
 			return error("unable to get sha1 of object %u in %s",
-				     pos, p->pack_name);
+				     index_pos, p->pack_name);
 
-		r = cb(&oid, p, pos, data);
+		r = cb(&oid, p, index_pos, data);
 		if (r)
 			break;
 	}