pack-objects: no crc check when the cached version is used

Current code makes pack-objects always do check_pack_crc() in
unpack_entry() even if right after that we find out there's a cached
version and pack access is not needed. Swap two code blocks, search
for cached version first, then check crc.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

sha1_file.c

@@ -2056,6 +2056,16 @@ void *unpack_entry(struct packed_git *p, off_t obj_offset,
 		int i;
 		struct delta_base_cache_entry *ent;
 
+		ent = get_delta_base_cache_entry(p, curpos);
+		if (eq_delta_base_cache_entry(ent, p, curpos)) {
+			type = ent->type;
+			data = ent->data;
+			size = ent->size;
+			clear_delta_base_cache_entry(ent);
+			base_from_cache = 1;
+			break;
+		}
+
 		if (do_check_packed_object_crc && p->index_version > 1) {
 			struct revindex_entry *revidx = find_pack_revindex(p, obj_offset);
 			unsigned long len = revidx[1].offset - obj_offset;
@@ -2070,16 +2080,6 @@ void *unpack_entry(struct packed_git *p, off_t obj_offset,
 			}
 		}
 
-		ent = get_delta_base_cache_entry(p, curpos);
-		if (eq_delta_base_cache_entry(ent, p, curpos)) {
-			type = ent->type;
-			data = ent->data;
-			size = ent->size;
-			clear_delta_base_cache_entry(ent);
-			base_from_cache = 1;
-			break;
-		}
-
 		type = unpack_object_header(p, &w_curs, &curpos, &size);
 		if (type != OBJ_OFS_DELTA && type != OBJ_REF_DELTA)
 			break;