send-pack/receive-pack: allow errors to be reported back to pusher.

This updates the protocol between git-send-pack/git-receive-pack
in a backward compatible way to allow failures at the receiving
end to be propagated back to the sender.  Most notably, versions
of git-push before this could not notice if the update hook on
the receiving end refused to update the ref for its own policy
reasons.

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 88 insertions, 32 deletions

diff --git a/receive-pack.c b/receive-pack.c
index 92878ecac3..e79de917b5 100644
--- a/receive-pack.c
+++ b/receive-pack.c
@@ -8,20 +8,33 @@ static const char receive_pack_usage[] = "git-receive-pack <git-dir>";
 
 static const char unpacker[] = "git-unpack-objects";
 
+static int report_status = 0;
+
+static char capabilities[] = "report-status";
+static int capabilities_sent = 0;
+
 static int show_ref(const char *path, const unsigned char *sha1)
 {
-	packet_write(1, "%s %s\n", sha1_to_hex(sha1), path);
+	if (capabilities_sent)
+		packet_write(1, "%s %s\n", sha1_to_hex(sha1), path);
+	else
+		packet_write(1, "%s %s%c%s\n",
+			     sha1_to_hex(sha1), path, 0, capabilities);
+	capabilities_sent = 1;
 	return 0;
 }
 
 static void write_head_info(void)
 {
 	for_each_ref(show_ref);
+	if (!capabilities_sent)
+		show_ref("capabilities^{}", null_sha1);
+
 }
 
 struct command {
 	struct command *next;
-	unsigned char updated;
+	const char *error_string;
 	unsigned char old_sha1[20];
 	unsigned char new_sha1[20];
 	char ref_name[0];
@@ -71,33 +84,37 @@ static int run_update_hook(const char *refname,
 	case 0:
 		return 0;
 	case -ERR_RUN_COMMAND_FORK:
-		die("hook fork failed");
+		return error("hook fork failed");
 	case -ERR_RUN_COMMAND_EXEC:
-		die("hook execute failed");
+		return error("hook execute failed");
 	case -ERR_RUN_COMMAND_WAITPID:
-		die("waitpid failed");
+		return error("waitpid failed");
 	case -ERR_RUN_COMMAND_WAITPID_WRONG_PID:
-		die("waitpid is confused");
+		return error("waitpid is confused");
 	case -ERR_RUN_COMMAND_WAITPID_SIGNAL:
-		fprintf(stderr, "%s died of signal\n", update_hook);
-		return -1;
+		return error("%s died of signal\n", update_hook);
 	case -ERR_RUN_COMMAND_WAITPID_NOEXIT:
-		die("%s died strangely", update_hook);
+		return error("%s died strangely", update_hook);
 	default:
 		error("%s exited with error code %d", update_hook, -code);
 		return -code;
 	}
 }
 
-static int update(const char *name,
-		  unsigned char *old_sha1, unsigned char *new_sha1)
+static int update(struct command *cmd)
 {
+	const char *name = cmd->ref_name;
+	unsigned char *old_sha1 = cmd->old_sha1;
+	unsigned char *new_sha1 = cmd->new_sha1;
 	char new_hex[60], *old_hex, *lock_name;
 	int newfd, namelen, written;
 
-	if (!strncmp(name, "refs/", 5) && check_ref_format(name + 5))
+	cmd->error_string = NULL;
+	if (!strncmp(name, "refs/", 5) && check_ref_format(name + 5)) {
+		cmd->error_string = "funny refname";
 		return error("refusing to create funny ref '%s' locally",
 			     name);
+	}
 
 	namelen = strlen(name);
 	lock_name = xmalloc(namelen + 10);
@@ -106,16 +123,19 @@ static int update(const char *name,
 
 	strcpy(new_hex, sha1_to_hex(new_sha1));
 	old_hex = sha1_to_hex(old_sha1);
-	if (!has_sha1_file(new_sha1))
+	if (!has_sha1_file(new_sha1)) {
+		cmd->error_string = "bad pack";
 		return error("unpack should have generated %s, "
 			     "but I can't find it!", new_hex);
-
+	}
 	safe_create_leading_directories(lock_name);
 
 	newfd = open(lock_name, O_CREAT | O_EXCL | O_WRONLY, 0666);
-	if (newfd < 0)
+	if (newfd < 0) {
+		cmd->error_string = "can't lock";
 		return error("unable to create %s (%s)",
 			     lock_name, strerror(errno));
+	}
 
 	/* Write the ref with an ending '\n' */
 	new_hex[40] = '\n';
@@ -127,18 +147,22 @@ static int update(const char *name,
 	close(newfd);
 	if (written != 41) {
 		unlink(lock_name);
+		cmd->error_string = "can't write";
 		return error("unable to write %s", lock_name);
 	}
 	if (verify_old_ref(name, old_hex) < 0) {
 		unlink(lock_name);
+		cmd->error_string = "raced";
 		return error("%s changed during push", name);
 	}
 	if (run_update_hook(name, old_hex, new_hex)) {
 		unlink(lock_name);
+		cmd->error_string = "hook declined";
 		return error("hook declined to update %s\n", name);
 	}
 	else if (rename(lock_name, name) < 0) {
 		unlink(lock_name);
+		cmd->error_string = "can't rename";
 		return error("unable to replace %s", name);
 	}
 	else {
@@ -158,7 +182,7 @@ static void run_update_post_hook(struct command *cmd)
 	if (access(update_post_hook, X_OK) < 0)
 		return;
 	for (argc = 1, cmd_p = cmd; cmd_p; cmd_p = cmd_p->next) {
-		if (!cmd_p->updated)
+		if (cmd_p->error_string)
 			continue;
 		argc++;
 	}
@@ -166,7 +190,7 @@ static void run_update_post_hook(struct command *cmd)
 	argv[0] = update_post_hook;
 
 	for (argc = 1, cmd_p = cmd; cmd_p; cmd_p = cmd_p->next) {
-		if (!cmd_p->updated)
+		if (cmd_p->error_string)
 			continue;
 		argv[argc] = xmalloc(strlen(cmd_p->ref_name) + 1);
 		strcpy(argv[argc], cmd_p->ref_name);
@@ -185,8 +209,7 @@ static void execute_commands(void)
 	struct command *cmd = commands;
 
 	while (cmd) {
-		cmd->updated = !update(cmd->ref_name,
-				       cmd->old_sha1, cmd->new_sha1);
+		update(cmd);
 		cmd = cmd->next;
 	}
 	run_update_post_hook(commands);
@@ -199,7 +222,8 @@ static void read_head_info(void)
 		static char line[1000];
 		unsigned char old_sha1[20], new_sha1[20];
 		struct command *cmd;
-		int len;
+		char *refname;
+		int len, reflen;
 
 		len = packet_read_line(0, line, sizeof(line));
 		if (!len)
@@ -211,38 +235,66 @@ static void read_head_info(void)
 		    line[81] != ' ' ||
 		    get_sha1_hex(line, old_sha1) ||
 		    get_sha1_hex(line + 41, new_sha1))
-			die("protocol error: expected old/new/ref, got '%s'", line);
+			die("protocol error: expected old/new/ref, got '%s'",
+			    line);
+
+		refname = line + 82;
+		reflen = strlen(refname);
+		if (reflen + 82 < len) {
+			if (strstr(refname + reflen + 1, "report-status"))
+				report_status = 1;
+		}
 		cmd = xmalloc(sizeof(struct command) + len - 80);
 		memcpy(cmd->old_sha1, old_sha1, 20);
 		memcpy(cmd->new_sha1, new_sha1, 20);
 		memcpy(cmd->ref_name, line + 82, len - 81);
+		cmd->error_string = "n/a (unpacker error)";
 		cmd->next = NULL;
 		*p = cmd;
 		p = &cmd->next;
 	}
 }
 
-static void unpack(void)
+static const char *unpack(int *error_code)
 {
 	int code = run_command(unpacker, NULL);
+
+	*error_code = 0;
 	switch (code) {
 	case 0:
-		return;
+		return NULL;
 	case -ERR_RUN_COMMAND_FORK:
-		die("unpack fork failed");
+		return "unpack fork failed";
 	case -ERR_RUN_COMMAND_EXEC:
-		die("unpack execute failed");
+		return "unpack execute failed";
 	case -ERR_RUN_COMMAND_WAITPID:
-		die("waitpid failed");
+		return "waitpid failed";
 	case -ERR_RUN_COMMAND_WAITPID_WRONG_PID:
-		die("waitpid is confused");
+		return "waitpid is confused";
 	case -ERR_RUN_COMMAND_WAITPID_SIGNAL:
-		die("%s died of signal", unpacker);
+		return "unpacker died of signal";
 	case -ERR_RUN_COMMAND_WAITPID_NOEXIT:
-		die("%s died strangely", unpacker);
+		return "unpacker died strangely";
 	default:
-		die("%s exited with error code %d", unpacker, -code);
+		*error_code = -code;
+		return "unpacker exited with error code";
+	}
+}
+
+static void report(const char *unpack_status)
+{
+	struct command *cmd;
+	packet_write(1, "unpack %s\n",
+		     unpack_status ? unpack_status : "ok");
+	for (cmd = commands; cmd; cmd = cmd->next) {
+		if (!cmd->error_string)
+			packet_write(1, "ok %s\n",
+				     cmd->ref_name);
+		else
+			packet_write(1, "ng %s %s\n",
+				     cmd->ref_name, cmd->error_string);
 	}
+	packet_flush(1);
 }
 
 int main(int argc, char **argv)
@@ -275,8 +327,12 @@ int main(int argc, char **argv)
 
 	read_head_info();
 	if (commands) {
-		unpack();
-		execute_commands();
+		int code;
+		const char *unpack_status = unpack(&code);
+		if (!unpack_status)
+			execute_commands();
+		if (report_status)
+			report(unpack_status);
 	}
 	return 0;
 }