[RFCv2 12/16] transport: get_refs_via_connect exchanges capabilities before refs.

[Stefan Beller <sbeller@google.com>]

Signed-off-by: Stefan Beller <sbeller@google.com>
---

Notes:
    A minor issue I am unsure about here is the
    line
    	&& transport->smart_options->transport_version)
    which could be prevented if we always set the transport_version
    in make_remote to be the default remote version.
    
    The advantage of having it always set in make_remote would
    be a cleaner mind model (the version set is always accurate)
    as opposed to now (version may be 0, then the default
    applies as we don't care enough to set a version)
    
    However I think the code may be more ugly if we were to
    always set the version in make_remote as then we would need
    to move the DEFAULT_TRANSPORT_VERSION define into remote.h
    or somewhere else (transport.h is not included in remote.c,
    I guess that's on purpose?)

 transport.c | 28 ++++++++++++++++++++++++----
 transport.h |  6 ++++++
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/transport.c b/transport.c
index b49fc60..ba40677 100644
--- a/transport.c
+++ b/transport.c
@@ -523,14 +523,33 @@ static int connect_setup(struct transport *transport, int for_push, int verbose)
 
 static struct ref *get_refs_via_connect(struct transport *transport, int for_push)
 {
+	struct transport_options options;
 	struct git_transport_data *data = transport->data;
 	struct ref *refs;
+	int version = DEFAULT_TRANSPORT_VERSION;
 
+	if (transport->smart_options
+	    && transport->smart_options->transport_version)
+		version = transport->smart_options->transport_version;
 	connect_setup(transport, for_push, 0);
-	get_remote_heads(data->fd[0], NULL, 0, &refs,
-			 for_push ? REF_NORMAL : 0,
-			 &data->extra_have,
-			 &data->shallow);
+	switch (version) {
+	case 2: /* first talk about capabilities, then get the heads */
+		get_remote_capabilities(data->fd[0], NULL, 0);
+		preselect_capabilities(&options);
+		if (transport->select_capabilities)
+			transport->select_capabilities(&options);
+		request_capabilities(data->fd[1], &options);
+		/* fall through */
+	case 1:
+		get_remote_heads(data->fd[0], NULL, 0, &refs,
+				 for_push ? REF_NORMAL : 0,
+				 &data->extra_have,
+				 &data->shallow);
+		break;
+	default:
+		die("BUG: Transport version %d not supported", version);
+		break;
+	}
 	data->got_remote_heads = 1;
 
 	return refs;
@@ -987,6 +1006,7 @@ struct transport *transport_get(struct remote *remote, const char *url)
 		struct git_transport_data *data = xcalloc(1, sizeof(*data));
 		ret->data = data;
 		ret->set_option = NULL;
+		ret->select_capabilities = NULL;
 		ret->get_refs_list = get_refs_via_connect;
 		ret->fetch = fetch_refs_via_pack;
 		ret->push_refs = git_transport_push;
diff --git a/transport.h b/transport.h
index 6095d7a..3e63efc 100644
--- a/transport.h
+++ b/transport.h
@@ -74,6 +74,12 @@ struct transport {
 	int (*fetch)(struct transport *transport, int refs_nr, struct ref **refs);
 
 	/**
+	 * A callback to select protocol options. Must be set if
+	 * the caller wants to change transport options.
+	 */
+	void (*select_capabilities)(struct transport_options *);
+
+	/**
 	 * Push the objects and refs. Send the necessary objects, and
 	 * then, for any refs where peer_ref is set and
 	 * peer_ref->new_sha1 is different from old_sha1, tell the
-- 
2.4.1.345.gab207b6.dirty