receive-pack: Send hook output over side band #2

If the client requests to enable side-band-64k capability we can
safely send any hook stdout or stderr data down side band #2,
so the client can present it to the user.

If side-band-64k isn't enabled, hooks continue to inherit stderr
from the parent receive-pack process.

When the side band channel is being used the push client will wind up
prefixing all server messages with "remote: ", just like fetch does,
so our test vector has to be updated with the new expected output.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/t5401-update-hooks.sh b/t/t5401-update-hooks.sh
index 64f66c9..c3cf397 100755
--- a/t/t5401-update-hooks.sh
+++ b/t/t5401-update-hooks.sh
@@ -118,19 +118,19 @@
 '
 
 cat <<EOF >expect
-STDOUT pre-receive
-STDERR pre-receive
-STDOUT update refs/heads/master
-STDERR update refs/heads/master
-STDOUT update refs/heads/tofail
-STDERR update refs/heads/tofail
-STDOUT post-receive
-STDERR post-receive
-STDOUT post-update
-STDERR post-update
+remote: STDOUT pre-receive
+remote: STDERR pre-receive
+remote: STDOUT update refs/heads/master
+remote: STDERR update refs/heads/master
+remote: STDOUT update refs/heads/tofail
+remote: STDERR update refs/heads/tofail
+remote: STDOUT post-receive
+remote: STDERR post-receive
+remote: STDOUT post-update
+remote: STDERR post-update
 EOF
 test_expect_success 'send-pack stderr contains hook messages' '
-	grep ^STD send.err >actual &&
+	grep ^remote: send.err | sed "s/ *\$//" >actual &&
 	test_cmp - actual <expect
 '