From efa3d64ce86a600563c8bf909c46dd0985ee6c11 Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Fri, 3 Sep 2021 11:06:37 +0200
Subject: update-ref: fix streaming of status updates

When executing git-update-ref(1) with the `--stdin` flag, then the user
can queue updates and, since e48cf33b61 (update-ref: implement
interactive transaction handling, 2020-04-02), interactively drive the
transaction's state via a set of transactional verbs. This interactivity
is somewhat broken though: while the caller can use these verbs to drive
the transaction's state, the status messages which confirm that a verb
has been processed is not flushed. The caller may thus be left hanging
waiting for the acknowledgement.

Fix the bug by flushing stdout after writing the status update. Add a
test which catches this bug.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 t/t1400-update-ref.sh | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

(limited to 't')

diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh
index 4506cd435b..1e754e258f 100755
--- a/t/t1400-update-ref.sh
+++ b/t/t1400-update-ref.sh
@@ -1598,6 +1598,38 @@ test_expect_success 'transaction cannot restart ongoing transaction' '
 	test_must_fail git show-ref --verify refs/heads/restart
 '
 
+test_expect_success PIPE 'transaction flushes status updates' '
+	mkfifo in out &&
+	(git update-ref --stdin <in >out &) &&
+
+	exec 9>in &&
+	test_when_finished "exec 9>&-" &&
+
+	echo "start" >&9 &&
+	echo "start: ok" >expected &&
+	read line <out &&
+	echo "$line" >actual &&
+	test_cmp expected actual &&
+
+	echo "create refs/heads/flush $A" >&9 &&
+
+	echo prepare >&9 &&
+	echo "prepare: ok" >expected &&
+	read line <out &&
+	echo "$line" >actual &&
+	test_cmp expected actual &&
+
+	# This must now fail given that we have locked the ref.
+	test_must_fail git update-ref refs/heads/flush $B 2>stderr &&
+	grep "fatal: update_ref failed for ref ${SQ}refs/heads/flush${SQ}: cannot lock ref" stderr &&
+
+	echo commit >&9 &&
+	echo "commit: ok" >expected &&
+	read line <out &&
+	echo "$line" >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'directory not created deleting packed ref' '
 	git branch d1/d2/r1 HEAD &&
 	git pack-refs --all &&
-- 
cgit v1.2.3


From 7c1200745bec3034c98d6e44bd5f620849dbe2ba Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Wed, 15 Sep 2021 13:24:52 -0400
Subject: t1400: avoid SIGPIPE race condition on fifo

t1400.190 sometimes fails or even hangs because of the way it uses
fifos. Our goal is to interactively read and write lines from
update-ref, so we have two fifos, in and out. We open a descriptor
connected to "in" and redirect output to that, so that update-ref does
not see EOF as it would if we opened and closed it for each "echo" call.

But we don't do the same for the output. This leads to a race where our
"read response <out" has not yet opened the fifo, but update-ref tries
to write to it and gets SIGPIPE. This can result in the test failing, or
worse, hanging as we wait forever for somebody to write to the pipe.

This is the same proble we fixed in 4783e7ea83 (t0008: avoid SIGPIPE
race condition on fifo, 2013-07-12), and we can fix it the same way, by
opening a second long-running descriptor.

Before this patch, running:

  ./t1400-update-ref.sh --run=1,190 --stress

failed or hung within a few dozen iterations. After it, I ran it for
several hundred without problems.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 t/t1400-update-ref.sh | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

(limited to 't')

diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh
index 1e754e258f..0d4f73acaa 100755
--- a/t/t1400-update-ref.sh
+++ b/t/t1400-update-ref.sh
@@ -1603,11 +1603,13 @@ test_expect_success PIPE 'transaction flushes status updates' '
 	(git update-ref --stdin <in >out &) &&
 
 	exec 9>in &&
+	exec 8<out &&
 	test_when_finished "exec 9>&-" &&
+	test_when_finished "exec 8<&-" &&
 
 	echo "start" >&9 &&
 	echo "start: ok" >expected &&
-	read line <out &&
+	read line <&8 &&
 	echo "$line" >actual &&
 	test_cmp expected actual &&
 
@@ -1615,7 +1617,7 @@ test_expect_success PIPE 'transaction flushes status updates' '
 
 	echo prepare >&9 &&
 	echo "prepare: ok" >expected &&
-	read line <out &&
+	read line <&8 &&
 	echo "$line" >actual &&
 	test_cmp expected actual &&
 
@@ -1625,7 +1627,7 @@ test_expect_success PIPE 'transaction flushes status updates' '
 
 	echo commit >&9 &&
 	echo "commit: ok" >expected &&
-	read line <out &&
+	read line <&8 &&
 	echo "$line" >actual &&
 	test_cmp expected actual
 '
-- 
cgit v1.2.3