merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/t/lib-terminal.sh

@@ -0,0 +1,36 @@
+# Helpers for terminal output tests.
+
+# Catch tests which should depend on TTY but forgot to. There's no need
+# to additionally check that the TTY prereq is set here.  If the test declared
+# it and we are running the test, then it must have been set.
+test_terminal () {
+	if ! test_declared_prereq TTY
+	then
+		echo >&4 "test_terminal: need to declare TTY prerequisite"
+		return 127
+	fi
+	perl "$TEST_DIRECTORY"/test-terminal.perl "$@" 2>&7
+} 7>&2 2>&4
+
+test_lazy_prereq TTY '
+	test_have_prereq PERL &&
+
+	# Reading from the pty master seems to get stuck _sometimes_
+	# on Mac OS X 10.5.0, using Perl 5.10.0 or 5.8.9.
+	#
+	# Reproduction recipe: run
+	#
+	#	i=0
+	#	while ./test-terminal.perl echo hi $i
+	#	do
+	#		: $((i = $i + 1))
+	#	done
+	#
+	# After 2000 iterations or so it hangs.
+	# https://rt.cpan.org/Ticket/Display.html?id=65692
+	#
+	test "$(uname -s)" != Darwin &&
+
+	perl "$TEST_DIRECTORY"/test-terminal.perl \
+		sh -c "test -t 1 && test -t 2"
+'