for_each_alternate_ref: pass name/oid instead of ref struct

Breaking down the fields in the interface makes it easier to
change the backend of for_each_alternate_ref to something
that doesn't use "struct ref" internally.

The only field that callers actually look at is the oid,
anyway. The refname is kept in the interface as a plausible
thing for future code to want.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/receive-pack.c

@@ -277,10 +277,12 @@ static int show_one_alternate_sha1(const unsigned char sha1[20], void *unused)
 	return 0;
 }
 
-static void collect_one_alternate_ref(const struct ref *ref, void *data)
+static void collect_one_alternate_ref(const char *refname,
+				      const struct object_id *oid,
+				      void *data)
 {
 	struct sha1_array *sa = data;
-	sha1_array_append(sa, ref->old_oid.hash);
+	sha1_array_append(sa, oid->hash);
 }
 
 static void write_head_info(void)

fetch-pack.c

@@ -253,9 +253,11 @@ static void send_request(struct fetch_pack_args *args,
 		write_or_die(fd, buf->buf, buf->len);
 }
 
-static void insert_one_alternate_ref(const struct ref *ref, void *unused)
+static void insert_one_alternate_ref(const char *refname,
+				     const struct object_id *oid,
+				     void *unused)
 {
-	rev_list_insert_ref(NULL, ref->old_oid.hash);
+	rev_list_insert_ref(NULL, oid->hash);
 }
 
 #define INITIAL_FLUSH 16
@@ -619,9 +621,11 @@ static void filter_refs(struct fetch_pack_args *args,
 	*refs = newlist;
 }
 
-static void mark_alternate_complete(const struct ref *ref, void *unused)
+static void mark_alternate_complete(const char *refname,
+				    const struct object_id *oid,
+				    void *unused)
 {
-	mark_complete(ref->old_oid.hash);
+	mark_complete(oid->hash);
 }
 
 static int everything_local(struct fetch_pack_args *args,

transport.c

@@ -1238,7 +1238,7 @@ static int refs_from_alternate_cb(struct alternate_object_database *e,
 	for (extra = transport_get_remote_refs(transport);
 	     extra;
 	     extra = extra->next)
-		cb->fn(extra, cb->data);
+		cb->fn(extra->name, &extra->old_oid, cb->data);
 	transport_disconnect(transport);
 out:
 	strbuf_release(&path);

transport.h

@@ -255,6 +255,6 @@ int transport_refs_pushed(struct ref *ref);
 void transport_print_push_status(const char *dest, struct ref *refs,
 		  int verbose, int porcelain, unsigned int *reject_reasons);
 
-typedef void alternate_ref_fn(const struct ref *, void *);
+typedef void alternate_ref_fn(const char *refname, const struct object_id *oid, void *);
 extern void for_each_alternate_ref(alternate_ref_fn, void *);
 #endif