atomic write for sideband remote messages

It has been a few times that I ended up with such a confusing display:

|remote: Generating pack...
|remote: Done counting 17 objects.
|remote: Result has 9 objects.
|remote: Deltifying 9 objects.
|remote:  100% (9/9) done
|remote: Unpacking 9 objects
|Total 9, written 9 (delta 8), reused 0 (delta 0)
| 100% (9/9) done

The confusion can be avoided in most cases by writing the remote message
in one go to prevent interleacing with local messages.  The buffer
declaration has been moved inside recv_sideband() to avoid extra string
copies.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

4 files changed, 19 insertions, 17 deletions

diff --git a/builtin-archive.c b/builtin-archive.c
index 6dabdee201..9177379122 100644
--- a/builtin-archive.c
+++ b/builtin-archive.c
@@ -75,7 +75,7 @@ static int run_remote_archiver(const char *remote, int argc,
 		die("git-archive: expected a flush");
 
 	/* Now, start reading from fd[0] and spit it out to stdout */
-	rv = recv_sideband("archive", fd[0], 1, 2, buf, sizeof(buf));
+	rv = recv_sideband("archive", fd[0], 1, 2);
 	close(fd[0]);
 	rv |= finish_connect(pid);
 
diff --git a/fetch-clone.c b/fetch-clone.c
index b632ca0438..76b99afcdb 100644
--- a/fetch-clone.c
+++ b/fetch-clone.c
@@ -115,12 +115,10 @@ static pid_t setup_sideband(int sideband, const char *me, int fd[2], int xd[2])
 		die("%s: unable to fork off sideband demultiplexer", me);
 	if (!side_pid) {
 		/* subprocess */
-		char buf[LARGE_PACKET_MAX];
-
 		close(fd[0]);
 		if (xd[0] != xd[1])
 			close(xd[1]);
-		if (recv_sideband(me, xd[0], fd[1], 2, buf, sizeof(buf)))
+		if (recv_sideband(me, xd[0], fd[1], 2))
 			exit(1);
 		exit(0);
 	}
diff --git a/sideband.c b/sideband.c
index 1b14ff8892..277fa3c10d 100644
--- a/sideband.c
+++ b/sideband.c
@@ -11,10 +11,13 @@
  * stream, aka "verbose").  A message over band #3 is a signal that
  * the remote died unexpectedly.  A flush() concludes the stream.
  */
-int recv_sideband(const char *me, int in_stream, int out, int err, char *buf, int bufsz)
+int recv_sideband(const char *me, int in_stream, int out, int err)
 {
+	char buf[7 + LARGE_PACKET_MAX + 1];
+	strcpy(buf, "remote:");
 	while (1) {
-		int len = packet_read_line(in_stream, buf, bufsz);
+		int band, len;
+		len	= packet_read_line(in_stream, buf+7, LARGE_PACKET_MAX);
 		if (len == 0)
 			break;
 		if (len < 1) {
@@ -22,25 +25,26 @@ int recv_sideband(const char *me, int in_stream, int out, int err, char *buf, in
 			safe_write(err, buf, len);
 			return SIDEBAND_PROTOCOL_ERROR;
 		}
+		band = buf[7] & 0xff;
 		len--;
-		switch (buf[0] & 0xFF) {
+		switch (band) {
 		case 3:
-			safe_write(err, "remote: ", 8);
-			safe_write(err, buf+1, len);
-			safe_write(err, "\n", 1);
+			buf[7] = ' ';
+			buf[8+len] = '\n';
+			safe_write(err, buf, 8+len+1);
 			return SIDEBAND_REMOTE_ERROR;
 		case 2:
-			safe_write(err, "remote: ", 8);
-			safe_write(err, buf+1, len);
+			buf[7] = ' ';
+			safe_write(err, buf, 8+len);
 			continue;
 		case 1:
-			safe_write(out, buf+1, len);
+			safe_write(out, buf+8, len);
 			continue;
 		default:
-			len = sprintf(buf + 1,
+			len = sprintf(buf,
 				      "%s: protocol error: bad band #%d\n",
-				      me, buf[0] & 0xFF);
-			safe_write(err, buf+1, len);
+				      me, band);
+			safe_write(err, buf, len);
 			return SIDEBAND_PROTOCOL_ERROR;
 		}
 	}
diff --git a/sideband.h b/sideband.h
index 4872106fa0..a84b6917c7 100644
--- a/sideband.h
+++ b/sideband.h
@@ -7,7 +7,7 @@
 #define DEFAULT_PACKET_MAX 1000
 #define LARGE_PACKET_MAX 65520
 
-int recv_sideband(const char *me, int in_stream, int out, int err, char *, int);
+int recv_sideband(const char *me, int in_stream, int out, int err);
 ssize_t send_sideband(int fd, int band, const char *data, ssize_t sz, int packet_max);
 
 #endif