sha1-file: add function to update existing loose object cache

Create a function to add a new object to the loose object cache
after the existing odb/xx/ directory was scanned.

This will be used in a later commit to keep the loose object
cache fresh after dynamically fetching an individual object
and without requiring the odb/xx/ directory to be rescanned.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>

object-file.c

@@ -2844,6 +2844,13 @@ struct oidtree *odb_loose_cache(struct object_directory *odb,
 	return odb->loose_objects_cache;
 }
 
+void odb_loose_cache_add_new_oid(struct object_directory *odb,
+				 const struct object_id *oid)
+{
+	struct oidtree *cache = odb_loose_cache(odb, oid);
+	append_loose_object(oid, NULL, cache);
+}
+
 void odb_clear_loose_cache(struct object_directory *odb)
 {
 	oidtree_clear(odb->loose_objects_cache);

object-store-ll.h

@@ -91,6 +91,14 @@ void restore_primary_odb(struct object_directory *restore_odb, const char *old_p
 struct oidtree *odb_loose_cache(struct object_directory *odb,
 				  const struct object_id *oid);
 
+/*
+ * Add a new object to the loose object cache (possibly after the
+ * cache was populated).  This might be used after dynamically
+ * fetching a missing object.
+ */
+void odb_loose_cache_add_new_oid(struct object_directory *odb,
+				 const struct object_id *oid);
+
 /* Empty the loose object cache for the specified object directory. */
 void odb_clear_loose_cache(struct object_directory *odb);