reference-transaction: use hook API instead of run-command

Convert the reference-transaction hook to the new hook API,
so it doesn't need to set up a struct child_process, call
find_hook or toggle the pipe signals.

The stdin feed callback is processing one ref update per
call. I haven't noticed any performance degradation due
to this, however we can batch as many we want in each call,
to ensure a good pipe throughtput (i.e. the child does not
wait after stdin).

Helped-by: Emily Shaffer <nasamuffin@google.com>
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: 10ne1

refs.c

@@ -2405,68 +2405,73 @@ static int ref_update_reject_duplicates(struct string_list *refnames,
 	return 0;
 }
 
-static int run_transaction_hook(struct ref_transaction *transaction,
-				const char *state)
+struct transaction_feed_cb_data {
+	size_t index;
+	struct strbuf buf;
+};
+
+static int transaction_hook_feed_stdin(int hook_stdin_fd, void *pp_cb, void *pp_task_cb UNUSED)
 {
-	struct child_process proc = CHILD_PROCESS_INIT;
-	struct strbuf buf = STRBUF_INIT;
-	const char *hook;
-	int ret = 0;
+	struct hook_cb_data *hook_cb = pp_cb;
+	struct run_hooks_opt *opt = hook_cb->options;
+	struct ref_transaction *transaction = opt->feed_pipe_ctx;
+	struct transaction_feed_cb_data *feed_cb_data = opt->feed_pipe_cb_data;
+	struct strbuf *buf = &feed_cb_data->buf;
+	struct ref_update *update;
+	size_t i = feed_cb_data->index++;
+	int ret;
 
-	hook = find_hook(transaction->ref_store->repo, "reference-transaction");
-	if (!hook)
-		return ret;
+	if (i >= transaction->nr)
+		return 1; /* No more refs to process */
 
-	strvec_pushl(&proc.args, hook, state, NULL);
-	proc.in = -1;
-	proc.stdout_to_stderr = 1;
-	proc.trace2_hook_name = "reference-transaction";
+	update = transaction->updates[i];
 
-	ret = start_command(&proc);
-	if (ret)
-		return ret;
+	if (update->flags & REF_LOG_ONLY)
+		return 0;
 
-	sigchain_push(SIGPIPE, SIG_IGN);
+	strbuf_reset(buf);
 
-	for (size_t i = 0; i < transaction->nr; i++) {
-		struct ref_update *update = transaction->updates[i];
+	if (!(update->flags & REF_HAVE_OLD))
+		strbuf_addf(buf, "%s ", oid_to_hex(null_oid(the_hash_algo)));
+	else if (update->old_target)
+		strbuf_addf(buf, "ref:%s ", update->old_target);
+	else
+		strbuf_addf(buf, "%s ", oid_to_hex(&update->old_oid));
 
-		if (update->flags & REF_LOG_ONLY)
-			continue;
+	if (!(update->flags & REF_HAVE_NEW))
+		strbuf_addf(buf, "%s ", oid_to_hex(null_oid(the_hash_algo)));
+	else if (update->new_target)
+		strbuf_addf(buf, "ref:%s ", update->new_target);
+	else
+		strbuf_addf(buf, "%s ", oid_to_hex(&update->new_oid));
 
-		strbuf_reset(&buf);
+	strbuf_addf(buf, "%s\n", update->refname);
 
-		if (!(update->flags & REF_HAVE_OLD))
-			strbuf_addf(&buf, "%s ", oid_to_hex(null_oid(the_hash_algo)));
-		else if (update->old_target)
-			strbuf_addf(&buf, "ref:%s ", update->old_target);
-		else
-			strbuf_addf(&buf, "%s ", oid_to_hex(&update->old_oid));
+	ret = write_in_full(hook_stdin_fd, buf->buf, buf->len);
+	if (ret < 0 && errno != EPIPE)
+		return ret;
 
-		if (!(update->flags & REF_HAVE_NEW))
-			strbuf_addf(&buf, "%s ", oid_to_hex(null_oid(the_hash_algo)));
-		else if (update->new_target)
-			strbuf_addf(&buf, "ref:%s ", update->new_target);
-		else
-			strbuf_addf(&buf, "%s ", oid_to_hex(&update->new_oid));
+	return 0; /* no more input to feed */
+}
+
+static int run_transaction_hook(struct ref_transaction *transaction,
+				const char *state)
+{
+	struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT;
+	struct transaction_feed_cb_data feed_ctx = { 0 };
+	int ret = 0;
 
-		strbuf_addf(&buf, "%s\n", update->refname);
+	strvec_push(&opt.args, state);
 
-		if (write_in_full(proc.in, buf.buf, buf.len) < 0) {
-			if (errno != EPIPE) {
-				/* Don't leak errno outside this API */
-				errno = 0;
-				ret = -1;
-			}
-			break;
-		}
-	}
+	opt.feed_pipe = transaction_hook_feed_stdin;
+	opt.feed_pipe_ctx = transaction;
+	opt.feed_pipe_cb_data = &feed_ctx;
 
-	close(proc.in);
-	sigchain_pop(SIGPIPE);
-	strbuf_release(&buf);
+	strbuf_init(&feed_ctx.buf, 0);
+
+	ret = run_hooks_opt(transaction->ref_store->repo, "reference-transaction", &opt);
 
-	ret |= finish_command(&proc);
+	strbuf_release(&feed_ctx.buf);
 	return ret;
 }