Move un-namespaced constant to internal header

FLAG_BITS only seems to be used internally

include/git2/common.h

@@ -83,8 +83,6 @@ GIT_BEGIN_DECL
  */
 #define GIT_OID_HEX_ZERO "0000000000000000000000000000000000000000"
 
-#define FLAG_BITS 27
-
 /**
  * Return the version of the libgit2 library
  * being currently used.

src/commit_list.h

@@ -18,6 +18,8 @@
 #define COMMIT_ALLOC \
 	(sizeof(git_commit_list_node) + PARENTS_PER_COMMIT * sizeof(git_commit_list_node *))
 
+#define FLAG_BITS 4
+
 typedef struct git_commit_list_node {
 	git_oid oid;
 	uint32_t time;