Remove some unused code

remote.go

diff --git a/remote.go b/remote.go
index 529bc39..585194e 100644
--- a/remote.go
+++ b/remote.go
@@ -166,19 +166,6 @@
 	return 0
 }
 
-type headlistData struct {
-	slice []*RemoteHead
-}
-
-func remoteHeadlistCb(rhead *C.git_remote_head, dataptr unsafe.Pointer) int {
-	data := (*headlistData)(dataptr)
-
-	head := newRemoteHeadFromC(rhead)
-	data.slice = append(data.slice, head)
-
-	return 0
-}
-
 func (r *Remote) Free() {
 	runtime.SetFinalizer(r, nil)
 	C.git_remote_free(r.ptr)