ssh: don't capture stderr

Don't capture stderr, optimize for the CLI case.

src/libgit2/transports/ssh_exec.c

@@ -45,8 +45,9 @@ static int ssh_exec_subtransport_stream_read(
 
 	transport = (ssh_exec_subtransport *)stream->parent.subtransport;
 
-	if ((ret = git_process_read(transport->process, buffer, buf_size)) < 0)
+	if ((ret = git_process_read(transport->process, buffer, buf_size)) < 0) {
 		return (int)ret;
+	}
 
 	*bytes_read = (size_t)ret;
 	return 0;
@@ -129,7 +130,7 @@ static int start_ssh(
 
 	process_opts.capture_in = 1;
 	process_opts.capture_out = 1;
-	process_opts.capture_err = 1;
+	process_opts.capture_err = 0;
 
 	switch (action) {
 	case GIT_SERVICE_UPLOADPACK_LS: