commit.h: reduce unnecessary includes

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/notes-utils.c b/notes-utils.c
index cb88171..4a793eb 100644
--- a/notes-utils.c
+++ b/notes-utils.c
@@ -6,6 +6,7 @@
 #include "refs.h"
 #include "notes-utils.h"
 #include "repository.h"
+#include "strbuf.h"
 
 void create_notes_commit(struct repository *r,
 			 struct notes_tree *t,