cbtree.h: define cb_init() in terms of CBTREE_INIT

Use the same pattern for cb_init() as the one established in the
recent refactoring of other such patterns in
5726a6b4012 (*.c *_init(): define in terms of corresponding *_INIT
macro, 2021-07-01).

It has been pointed out[1] that we could perhaps use this C99
replacement of using a compound literal for all of these:

    *t = (struct cb_tree){ 0 };

But let's just stick to the existing pattern established in
5726a6b4012 for now, we can leave another weather balloon for some
other time.

1. http://lore.kernel.org/git/ef724a3a-a4b8-65d3-c928-13a7d78f189a@gmail.com

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/cbtree.h b/cbtree.h
index a04a312c3f..dedbb8e2a4 100644
--- a/cbtree.h
+++ b/cbtree.h
@@ -37,11 +37,12 @@ enum cb_next {
 	CB_BREAK = 1
 };
 
-#define CBTREE_INIT { .root = NULL }
+#define CBTREE_INIT { 0 }
 
 static inline void cb_init(struct cb_tree *t)
 {
-	t->root = NULL;
+	struct cb_tree blank = CBTREE_INIT;
+	memcpy(t, &blank, sizeof(*t));
 }
 
 struct cb_node *cb_lookup(struct cb_tree *, const uint8_t *k, size_t klen);