for_each_*_object: store flag definitions in a single location

These flags were split between cache.h and packfile.h,
because some of the flags apply only to packs. However, they
share a single numeric namespace, since both are respected
for the packed variant. Let's make sure they're defined
together so that nobody accidentally adds a new flag in one
location that duplicates the other.

While we're here, let's also put them in an enum (which
helps debugger visibility) and use "(1<<n)" rather than
counting powers of 2 manually.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -1623,12 +1623,23 @@ int for_each_loose_file_in_objdir_buf(struct strbuf *path,
 				      each_loose_subdir_fn subdir_cb,
 				      void *data);
 
+/*
+ * Flags for for_each_*_object(), including for_each_loose below and
+ * for_each_packed in packfile.h.
+ */
+enum for_each_object_flags {
+	/* Iterate only over local objects, not alternates. */
+	FOR_EACH_OBJECT_LOCAL_ONLY = (1<<0),
+
+	/* Only iterate over packs obtained from the promisor remote. */
+	FOR_EACH_OBJECT_PROMISOR_ONLY = (1<<1),
+};
+
 /*
  * Iterate over loose objects in both the local
  * repository and any alternates repositories (unless the
  * LOCAL_ONLY flag is set).
  */
-#define FOR_EACH_OBJECT_LOCAL_ONLY 0x1
 extern int for_each_loose_object(each_loose_object_fn, void *, unsigned flags);
 
 /*