Compilation errors in git.pu/refs/reftable-backend.c

["Torsten Bögershausen" <tboegi@web.de>]

Folks, after the integration of the reftable branch:
Merge branch 'hn/reftable' into pu

My historic (?) compiler stumbles over this code here:
refs/reftable-backend.c
   for (int i = 0; i < transaction->nr; i++) {

So I think we could easily avoid the (for int i) construction.
The other observation could be, why we use an "int", when "nr" is
defined as a size_t ?

struct ref_transaction {
	struct ref_store *ref_store;
	struct ref_update **updates;
	size_t alloc;
	size_t nr;
	enum ref_transaction_state state;
	void *backend_data;
};

Thanks for working on Git