receive-pack: gently write messages to proc-receive

Johannes found a flaky hang in `t5411/test-0013-bad-protocol.sh` in the
osx-clang job of the CI/PR builds, and ran into an issue when using
the `--stress` option with the following error messages:

    fatal: unable to write flush packet: Broken pipe
    send-pack: unexpected disconnect while reading sideband packet
    fatal: the remote end hung up unexpectedly

In this test case, the "proc-receive" hook sends an error message and
dies earlier. While "receive-pack" on the other side of the pipe
should forward the error message of the "proc-receive" hook to the
client side, but it fails to do so. This is because "receive-pack"
uses `packet_write_fmt()` and `packet_flush()` to write pkt-line
message to "proc-receive" hook, and these functions die immediately
when pipe is broken. Using "gently" forms for these functions will get
more predicable output.

Add more "--die-*" options to test helper to test different stages of
the protocol between "receive-pack" and "proc-receive" hook.

Reported-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 63 insertions, 24 deletions

diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index bb9909c52e..2bd736525f 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -977,15 +977,25 @@ static int read_proc_receive_report(struct packet_reader *reader,
 	int new_report = 0;
 	int code = 0;
 	int once = 0;
+	int response = 0;
 
 	for (;;) {
 		struct object_id old_oid, new_oid;
 		const char *head;
 		const char *refname;
 		char *p;
-
-		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
+		enum packet_read_status status;
+
+		status = packet_reader_read(reader);
+		if (status != PACKET_READ_NORMAL) {
+			/* Check whether proc-receive exited abnormally */
+			if (status == PACKET_READ_EOF && !response) {
+				strbuf_addstr(errmsg, "proc-receive exited abnormally");
+				return -1;
+			}
 			break;
+		}
+		response++;
 
 		head = reader->line;
 		p = strchr(head, ' ');
@@ -1145,28 +1155,41 @@ static int run_proc_receive_hook(struct command *commands,
 	if (use_push_options)
 		strbuf_addstr(&cap, " push-options");
 	if (cap.len) {
-		packet_write_fmt(proc.in, "version=1%c%s\n", '\0', cap.buf + 1);
+		code = packet_write_fmt_gently(proc.in, "version=1%c%s\n", '\0', cap.buf + 1);
 		strbuf_release(&cap);
 	} else {
-		packet_write_fmt(proc.in, "version=1\n");
+		code = packet_write_fmt_gently(proc.in, "version=1\n");
 	}
-	packet_flush(proc.in);
+	if (!code)
+		code = packet_flush_gently(proc.in);
 
-	for (;;) {
-		int linelen;
+	if (!code)
+		for (;;) {
+			int linelen;
+			enum packet_read_status status;
 
-		if (packet_reader_read(&reader) != PACKET_READ_NORMAL)
-			break;
+			status = packet_reader_read(&reader);
+			if (status != PACKET_READ_NORMAL) {
+				/* Check whether proc-receive exited abnormally */
+				if (status == PACKET_READ_EOF)
+					code = -1;
+				break;
+			}
 
-		if (reader.pktlen > 8 && starts_with(reader.line, "version=")) {
-			version = atoi(reader.line + 8);
-			linelen = strlen(reader.line);
-			if (linelen < reader.pktlen) {
-				const char *feature_list = reader.line + linelen + 1;
-				if (parse_feature_request(feature_list, "push-options"))
-					hook_use_push_options = 1;
+			if (reader.pktlen > 8 && starts_with(reader.line, "version=")) {
+				version = atoi(reader.line + 8);
+				linelen = strlen(reader.line);
+				if (linelen < reader.pktlen) {
+					const char *feature_list = reader.line + linelen + 1;
+					if (parse_feature_request(feature_list, "push-options"))
+						hook_use_push_options = 1;
+				}
 			}
 		}
+
+	if (code) {
+		strbuf_addstr(&errmsg, "fail to negotiate version with proc-receive hook");
+		goto cleanup;
 	}
 
 	if (version != 1) {
@@ -1180,20 +1203,36 @@ static int run_proc_receive_hook(struct command *commands,
 	for (cmd = commands; cmd; cmd = cmd->next) {
 		if (!cmd->run_proc_receive || cmd->skip_update || cmd->error_string)
 			continue;
-		packet_write_fmt(proc.in, "%s %s %s",
-				 oid_to_hex(&cmd->old_oid),
-				 oid_to_hex(&cmd->new_oid),
-				 cmd->ref_name);
+		code = packet_write_fmt_gently(proc.in, "%s %s %s",
+					       oid_to_hex(&cmd->old_oid),
+					       oid_to_hex(&cmd->new_oid),
+					       cmd->ref_name);
+		if (code)
+			break;
+	}
+	if (!code)
+		code = packet_flush_gently(proc.in);
+	if (code) {
+		strbuf_addstr(&errmsg, "fail to write commands to proc-receive hook");
+		goto cleanup;
 	}
-	packet_flush(proc.in);
 
 	/* Send push options */
 	if (hook_use_push_options) {
 		struct string_list_item *item;
 
-		for_each_string_list_item(item, push_options)
-			packet_write_fmt(proc.in, "%s", item->string);
-		packet_flush(proc.in);
+		for_each_string_list_item(item, push_options) {
+			code = packet_write_fmt_gently(proc.in, "%s", item->string);
+			if (code)
+				break;
+		}
+		if (!code)
+			code = packet_flush_gently(proc.in);
+		if (code) {
+			strbuf_addstr(&errmsg,
+				      "fail to write push-options to proc-receive hook");
+			goto cleanup;
+		}
 	}
 
 	/* Read result from proc-receive */