transport: make transport vtable more privatejt/transport-hide-vtable

Move the definition of the transport-specific functions provided by
transports, whether declared in transport.c or transport-helper.c, into
an internal header. This means that transport-using code (as opposed to
transport-declaring code) can no longer access these functions (without
importing the internal header themselves), making it clear that they
should use the transport_*() functions instead, and also allowing the
interface between the transport mechanism and an individual transport to
independently evolve.

This is superficially a reversal of commit 824d5776c3f2 ("Refactor
struct transport_ops inlined into struct transport", 2007-09-19).
However, the scope of the involved variables was neither affected nor
discussed in that commit, and I think that the advantages in making
those functions more private outweigh the advantages described in that
commit's commit message. A minor additional point is that the code has
gotten more complicated since then, in that the function-pointer
variables are potentially mutated twice (once initially and once if
transport_take_over() is invoked), increasing the value of corralling
them into their own struct.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 9 deletions

diff --git a/transport-helper.c b/transport-helper.c
index c948d5215c..1a4b43ff15 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -11,6 +11,7 @@
 #include "sigchain.h"
 #include "argv-array.h"
 #include "refs.h"
+#include "transport-internal.h"
 
 static int debug;
 
@@ -650,7 +651,7 @@ static int fetch(struct transport *transport,
 
 	if (process_connect(transport, 0)) {
 		do_take_over(transport);
-		return transport->fetch(transport, nr_heads, to_fetch);
+		return transport->vtable->fetch(transport, nr_heads, to_fetch);
 	}
 
 	count = 0;
@@ -987,7 +988,7 @@ static int push_refs(struct transport *transport,
 
 	if (process_connect(transport, 1)) {
 		do_take_over(transport);
-		return transport->push_refs(transport, remote_refs, flags);
+		return transport->vtable->push_refs(transport, remote_refs, flags);
 	}
 
 	if (!remote_refs) {
@@ -1035,7 +1036,7 @@ static struct ref *get_refs_list(struct transport *transport, int for_push)
 
 	if (process_connect(transport, for_push)) {
 		do_take_over(transport);
-		return transport->get_refs_list(transport, for_push);
+		return transport->vtable->get_refs_list(transport, for_push);
 	}
 
 	if (data->push && for_push)
@@ -1084,6 +1085,15 @@ static struct ref *get_refs_list(struct transport *transport, int for_push)
 	return ret;
 }
 
+static struct transport_vtable vtable = {
+	set_helper_option,
+	get_refs_list,
+	fetch,
+	push_refs,
+	connect_helper,
+	release_helper
+};
+
 int transport_helper_init(struct transport *transport, const char *name)
 {
 	struct helper_data *data = xcalloc(1, sizeof(*data));
@@ -1095,12 +1105,7 @@ int transport_helper_init(struct transport *transport, const char *name)
 		debug = 1;
 
 	transport->data = data;
-	transport->set_option = set_helper_option;
-	transport->get_refs_list = get_refs_list;
-	transport->fetch = fetch;
-	transport->push_refs = push_refs;
-	transport->disconnect = release_helper;
-	transport->connect = connect_helper;
+	transport->vtable = &vtable;
 	transport->smart_options = &(data->transport_options);
 	return 0;
 }