Get the remote repository's reference advertisement list
Get the list of references with which the server responds to a new connection.
The remote (or more exactly its transport) must have connected to the remote repository. This list is available as soon as the connection to the remote is initiated and it remains available after disconnecting.
The memory belongs to the remote. The pointer will be valid as long as a new connection is not initiated, but it is recommended that you make a copy in order to make use of the data.
the number of remote heads
0 on success, or an error code