t/t7407: demonstrate that the command called by 'submodule foreach' loses stdin

The user-supplied command spawned by 'submodule foreach' loses its
connection to the original standard input.  Instead, it is connected to the
output of a pipe within the git-submodule script.  This can cause a problem
if the command requires reading from stdin or if it changes its behavior
based on whether stdin is a tty or not (e.g. git shortlog).  Demonstrate
this flaw.

Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7407-submodule-foreach.sh

@@ -288,4 +288,22 @@ test_expect_success 'use "update --recursive nested1" to checkout all submodules
 	)
 '
 
+test_expect_failure 'command passed to foreach retains notion of stdin' '
+	(
+		cd super &&
+		git submodule foreach echo success >../expected &&
+		yes | git submodule foreach "read y && test \"x\$y\" = xy && echo success" >../actual
+	) &&
+	test_cmp expected actual
+'
+
+test_expect_failure 'command passed to foreach --recursive retains notion of stdin' '
+	(
+		cd clone2 &&
+		git submodule foreach --recursive echo success >../expected &&
+		yes | git submodule foreach --recursive "read y && test \"x\$y\" = xy && echo success" >../actual
+	) &&
+	test_cmp expected actual
+'
+
 test_done