t7527: improve implicit shutdown testing in fsmonitor--daemon

Refactor the tests that exercise implicit shutdown cases
to make them more robust and less racy.

The fsmonitor--daemon will implicitly shutdown in a variety
of situations, such as when the ".git" directory is deleted
or renamed.

The existing tests would delete or rename the directory, sleep
for one second, and then check the status of the daemon.  This
is racy, since the client/status command has no way to sync
with the daemon.  This was noticed occasionally on very slow
CI build machines where it would cause a random test to fail.

Replace the simple sleep with a sleep-and-retry loop.

Signed-off-by: Jeff Hostetler <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: jeffhostetler

t/t7527-builtin-fsmonitor.sh

@@ -124,6 +124,36 @@ test_expect_success 'implicit daemon start' '
 	test_must_fail git -C test_implicit fsmonitor--daemon status
 '
 
+# Verify that the daemon has shutdown.  Spin a few seconds to
+# make the test a little more robust during CI testing.
+#
+# We're looking for an implicit shutdown, such as when we delete or
+# rename the ".git" directory.  Our delete/rename will cause a file
+# system event that the daemon will see and the daemon will
+# auto-shutdown as soon as it sees it.  But this is racy with our `git
+# fsmonitor--daemon status` commands (and we cannot use a cookie file
+# here to help us).  So spin a little and give the daemon a chance to
+# see the event.  (This is primarily for underpowered CI build/test
+# machines (where it might take a moment to wake and reschedule the
+# daemon process) to avoid false alarms during test runs.)
+#
+IMPLICIT_TIMEOUT=5
+
+verify_implicit_shutdown () {
+	r=$1 &&
+
+	k=0 &&
+	while test "$k" -lt $IMPLICIT_TIMEOUT
+	do
+		git -C $r fsmonitor--daemon status || return 0
+
+		sleep 1
+		k=$(( $k + 1 ))
+	done &&
+
+	return 1
+}
+
 test_expect_success 'implicit daemon stop (delete .git)' '
 	test_when_finished "stop_daemon_delete_repo test_implicit_1" &&
 
@@ -142,10 +172,9 @@ test_expect_success 'implicit daemon stop (delete .git)' '
 	#     This would make the test result dependent upon whether we
 	#     were using fsmonitor on our development worktree.
 	#
-	sleep 1 &&
 	mkdir test_implicit_1/.git &&
 
-	test_must_fail git -C test_implicit_1 fsmonitor--daemon status
+	verify_implicit_shutdown test_implicit_1
 '
 
 test_expect_success 'implicit daemon stop (rename .git)' '
@@ -160,10 +189,9 @@ test_expect_success 'implicit daemon stop (rename .git)' '
 
 	# See [1] above.
 	#
-	sleep 1 &&
 	mkdir test_implicit_2/.git &&
 
-	test_must_fail git -C test_implicit_2 fsmonitor--daemon status
+	verify_implicit_shutdown test_implicit_2
 '
 
 # File systems on Windows may or may not have shortnames.
@@ -194,13 +222,11 @@ test_expect_success MINGW,SHORTNAMES 'implicit daemon stop (rename GIT~1)' '
 	#
 	mv test_implicit_1s/GIT~1 test_implicit_1s/.gitxyz &&
 
-	sleep 1 &&
-	# put it back so that our status will not crawl out to our
-	# parent directory.
+	# See [1] above.
 	# this moves {.gitxyz, GITXYZ~1} to {.git, GIT~1}.
 	mv test_implicit_1s/.gitxyz test_implicit_1s/.git &&
 
-	test_must_fail git -C test_implicit_1s fsmonitor--daemon status
+	verify_implicit_shutdown test_implicit_1s
 '
 
 # Here we first create a file with LONGNAME of "GIT~1" before
@@ -223,12 +249,10 @@ test_expect_success MINGW,SHORTNAMES 'implicit daemon stop (rename GIT~2)' '
 	#
 	mv test_implicit_1s2/GIT~2 test_implicit_1s2/.gitxyz &&
 
-	sleep 1 &&
-	# put it back so that our status will not crawl out to our
-	# parent directory.
+	# See [1] above.
 	mv test_implicit_1s2/.gitxyz test_implicit_1s2/.git &&
 
-	test_must_fail git -C test_implicit_1s2 fsmonitor--daemon status
+	verify_implicit_shutdown test_implicit_1s2
 '
 
 test_expect_success 'cannot start multiple daemons' '
@@ -905,9 +929,11 @@ test_expect_success CASE_INSENSITIVE_FS 'case insensitive+preserving' '
 	# Rename .git using an alternate spelling to verify that that
 	# daemon detects it and automatically shuts down.
 	mv test_insensitive/.GIT test_insensitive/.FOO &&
-	sleep 1 &&
+
+	# See [1] above.
 	mv test_insensitive/.FOO test_insensitive/.git &&
-	test_must_fail git -C test_insensitive fsmonitor--daemon status &&
+
+	verify_implicit_shutdown test_insensitive &&
 
 	# Verify that events were reported using on-disk spellings of the
 	# directories and files that we touched.  We may or may not get a