transport-helper: use the new done feature where possible

In other words, use fast-export --use-done-feature to add a 'done'
command at the end of streams passed to remote helpers' "import"
commands, and teach the remote helpers implementing "export" to use
the 'done' command in turn when producing their streams.

The trailing \n in the protocol signals the helper that the
connection is about to close, allowing it to do whatever cleanup
neccesary.

Previously, the connection would already be closed by the
time the trailing \n was to be written. Now that the remote-helper
protocol uses the new done command in its fast-import streams, this
is no longer the case and we can safely write the trailing \n.

Signed-off-by: Sverre Rabbelier <srabbelier@gmail.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-remote-testgit.py

@@ -123,6 +123,8 @@ def do_import(repo, args):
     repo = update_local_repo(repo)
     repo.exporter.export_repo(repo.gitdir, args)
 
+    print "done"
+
 
 def do_export(repo, args):
     """Imports a fast-import stream from git to testgit.

transport-helper.c

@@ -380,8 +380,9 @@ static int get_exporter(struct transport *transport,
 	/* we need to duplicate helper->in because we want to use it after
 	 * fastexport is done with it. */
 	fastexport->out = dup(helper->in);
-	fastexport->argv = xcalloc(4 + revlist_args->nr, sizeof(*fastexport->argv));
+	fastexport->argv = xcalloc(5 + revlist_args->nr, sizeof(*fastexport->argv));
 	fastexport->argv[argc++] = "fast-export";
+	fastexport->argv[argc++] = "--use-done-feature";
 	if (export_marks)
 		fastexport->argv[argc++] = export_marks;
 	if (import_marks)
@@ -417,11 +418,8 @@ static int fetch_with_import(struct transport *transport,
 		sendline(data, &buf);
 		strbuf_reset(&buf);
 	}
-	if (disconnect_helper(transport))
-		die("Error while disconnecting helper");
 	if (finish_command(&fastimport))
 		die("Error while running fast-import");
-
 	free(fastimport.argv);
 	fastimport.argv = NULL;
 
@@ -764,11 +762,8 @@ static int push_refs_with_export(struct transport *transport,
 			 export_marks, import_marks, &revlist_args))
 		die("Couldn't run fast-export");
 
-	data->no_disconnect_req = 1;
 	if (finish_command(&exporter))
 		die("Error while running fast-export");
-	if (disconnect_helper(transport))
-		die("Error while disconnecting helper");
 	return 0;
 }