alloc: add repository argument to alloc_tree_node

This is a small mechanical change; it doesn't change the
implementation to handle repositories other than the_repository yet.
Use a macro to catch callers passing a repository other than
the_repository at compile time.
Signed-off-by: NStefan Beller <sbeller@google.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

alloc.c

@@ -57,7 +57,7 @@ void *alloc_blob_node_the_repository(void)
 }
 
 static struct alloc_state tree_state;
-void *alloc_tree_node(void)
+void *alloc_tree_node_the_repository(void)
 {
 	struct tree *t = alloc_node(&tree_state, sizeof(struct tree));
 	t->object.type = OBJ_TREE;

cache.h

@@ -1766,7 +1766,8 @@ void encode_85(char *buf, const unsigned char *data, int bytes);
 /* alloc.c */
 #define alloc_blob_node(r) alloc_blob_node_##r()
 extern void *alloc_blob_node_the_repository(void);
-extern void *alloc_tree_node(void);
+#define alloc_tree_node(r) alloc_tree_node_##r()
+extern void *alloc_tree_node_the_repository(void);
 extern void *alloc_commit_node(void);
 extern void *alloc_tag_node(void);
 extern void *alloc_object_node(void);

tree.c

@@ -197,7 +197,7 @@ struct tree *lookup_tree(const struct object_id *oid)
 	struct object *obj = lookup_object(oid->hash);
 	if (!obj)
 		return create_object(the_repository, oid->hash,
-				     alloc_tree_node());
+				     alloc_tree_node(the_repository));
 	return object_as_type(obj, OBJ_TREE, 0);
 }