object: remove "used" field from struct object

The "used" field in struct object is only used by builtin/fsck. Remove
that field and modify builtin/fsck to use a flag instead.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fsck.c

@@ -19,6 +19,8 @@
 #define REACHABLE 0x0001
 #define SEEN      0x0002
 #define HAS_OBJ   0x0004
+/* This flag is set if something points to this object. */
+#define USED      0x0008
 
 static int show_root;
 static int show_tags;
@@ -195,7 +197,7 @@ static int mark_used(struct object *obj, int type, void *data, struct fsck_optio
 {
 	if (!obj)
 		return 1;
-	obj->used = 1;
+	obj->flags |= USED;
 	return 0;
 }
 
@@ -244,7 +246,7 @@ static void check_unreachable_object(struct object *obj)
 	}
 
 	/*
-	 * "!used" means that nothing at all points to it, including
+	 * "!USED" means that nothing at all points to it, including
 	 * other unreachable objects. In other words, it's the "tip"
 	 * of some set of unreachable objects, usually a commit that
 	 * got dropped.
@@ -255,7 +257,7 @@ static void check_unreachable_object(struct object *obj)
 	 * deleted a branch by mistake, this is a prime candidate to
 	 * start looking at, for example.
 	 */
-	if (!obj->used) {
+	if (!(obj->flags & USED)) {
 		if (show_dangling)
 			printf("dangling %s %s\n", printable_type(obj),
 			       describe_object(obj));
@@ -379,7 +381,8 @@ static int fsck_obj_buffer(const struct object_id *oid, enum object_type type,
 		errors_found |= ERROR_OBJECT;
 		return error("%s: object corrupt or missing", oid_to_hex(oid));
 	}
-	obj->flags = HAS_OBJ;
+	obj->flags &= ~(REACHABLE | SEEN);
+	obj->flags |= HAS_OBJ;
 	return fsck_obj(obj);
 }
 
@@ -397,7 +400,7 @@ static void fsck_handle_reflog_oid(const char *refname, struct object_id *oid,
 				add_decoration(fsck_walk_options.object_names,
 					obj,
 					xstrfmt("%s@{%"PRItime"}", refname, timestamp));
-			obj->used = 1;
+			obj->flags |= USED;
 			mark_object_reachable(obj);
 		} else {
 			error("%s: invalid reflog entry %s", refname, oid_to_hex(oid));
@@ -445,7 +448,7 @@ static int fsck_handle_ref(const char *refname, const struct object_id *oid,
 		errors_found |= ERROR_REFS;
 	}
 	default_refs++;
-	obj->used = 1;
+	obj->flags |= USED;
 	if (name_objects)
 		add_decoration(fsck_walk_options.object_names,
 			obj, xstrdup(refname));
@@ -513,7 +516,8 @@ static int fsck_loose(const struct object_id *oid, const char *path, void *data)
 		return 0; /* keep checking other objects */
 	}
 
-	obj->flags = HAS_OBJ;
+	obj->flags &= ~(REACHABLE | SEEN);
+	obj->flags |= HAS_OBJ;
 	if (fsck_obj(obj))
 		errors_found |= ERROR_OBJECT;
 	return 0;
@@ -595,7 +599,7 @@ static int fsck_cache_tree(struct cache_tree *it)
 			errors_found |= ERROR_REFS;
 			return 1;
 		}
-		obj->used = 1;
+		obj->flags |= USED;
 		if (name_objects)
 			add_decoration(fsck_walk_options.object_names,
 				obj, xstrdup(":"));
@@ -737,7 +741,7 @@ int cmd_fsck(int argc, const char **argv, const char *prefix)
 				continue;
 			}
 
-			obj->used = 1;
+			obj->flags |= USED;
 			if (name_objects)
 				add_decoration(fsck_walk_options.object_names,
 					obj, xstrdup(arg));
@@ -774,7 +778,7 @@ int cmd_fsck(int argc, const char **argv, const char *prefix)
 			if (!blob)
 				continue;
 			obj = &blob->object;
-			obj->used = 1;
+			obj->flags |= USED;
 			if (name_objects)
 				add_decoration(fsck_walk_options.object_names,
 					obj,

object.c

@@ -141,7 +141,6 @@ void *create_object(const unsigned char *sha1, void *o)
 	struct object *obj = o;
 
 	obj->parsed = 0;
-	obj->used = 0;
 	obj->flags = 0;
 	hashcpy(obj->oid.hash, sha1);
 

object.h

@@ -38,6 +38,7 @@ struct object_array {
  * http-push.c:                            16-----19
  * commit.c:                               16-----19
  * sha1_name.c:                                     20
+ * builtin/fsck.c:  0--3
  */
 #define FLAG_BITS  27
 
@@ -46,7 +47,6 @@ struct object_array {
  */
 struct object {
 	unsigned parsed : 1;
-	unsigned used : 1;
 	unsigned type : TYPE_BITS;
 	unsigned flags : FLAG_BITS;
 	struct object_id oid;