object-store: allow fetching objects via has_object()

We're about to fully remove `repo_has_object_file()` in favor of
`has_object()`. The latter function does not yet have a way to fetch
missing objects via a promisor remote though, which means that it cannot
fully replace all usecases of `repo_has_object_file()`.

Introduce a new flag `HAS_OBJECT_FETCH_PROMISOR` that causes the
function to optionally fetch missing objects which are part of a
promisor pack. This flag will be used in the subsequent commit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

object-store.c

@@ -937,12 +937,15 @@ void *read_object_with_reference(struct repository *r,
 int has_object(struct repository *r, const struct object_id *oid,
 	       unsigned flags)
 {
-	int quick = !(flags & HAS_OBJECT_RECHECK_PACKED);
-	unsigned object_info_flags = OBJECT_INFO_SKIP_FETCH_OBJECT |
-		(quick ? OBJECT_INFO_QUICK : 0);
+	unsigned object_info_flags = 0;
 
 	if (!startup_info->have_repository)
 		return 0;
+	if (!(flags & HAS_OBJECT_RECHECK_PACKED))
+		object_info_flags |= OBJECT_INFO_QUICK;
+	if (!(flags & HAS_OBJECT_FETCH_PROMISOR))
+		object_info_flags |= OBJECT_INFO_SKIP_FETCH_OBJECT;
+
 	return oid_object_info_extended(r, oid, NULL, object_info_flags) >= 0;
 }
 

object-store.h

@@ -262,12 +262,16 @@ int oid_object_info_extended(struct repository *r,
 			     const struct object_id *,
 			     struct object_info *, unsigned flags);
 
-/* Retry packed storage after checking packed and loose storage */
-#define HAS_OBJECT_RECHECK_PACKED 1
+enum {
+	/* Retry packed storage after checking packed and loose storage */
+	HAS_OBJECT_RECHECK_PACKED = (1 << 0),
+	/* Allow fetching the object in case the repository has a promisor remote. */
+	HAS_OBJECT_FETCH_PROMISOR = (1 << 1),
+};
 
 /*
  * Returns 1 if the object exists. This function will not lazily fetch objects
- * in a partial clone.
+ * in a partial clone by default.
  */
 int has_object(struct repository *r, const struct object_id *oid,
 	       unsigned flags);