handle multibyte characters in name

Many "git submodule" operations do not work on a submodule at a path whose
name is not in ASCII.

This is because "git ls-files" is used to find which paths are bound to
submodules to the current working tree, and the output is C-quoted by default
for non ASCII pathnames.

Tell "git ls-files" to not C-quote its output, which is easier than unwrapping
C-quote ourselves.

Signed-off-by: Fredrik Gustafsson <iveqy@iveqy.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7400-submodule-basic.sh

@@ -868,4 +868,16 @@ test_expect_success 'submodule deinit fails when submodule has a .git directory
 	test -n "$(git config --get-regexp "submodule\.example\.")"
 '
 
+test_expect_success 'submodule with strange name works "å äö"' '
+	mkdir "å äö" &&
+	(
+		cd "å äö" &&
+		git init &&
+		touch sub
+		git add sub
+		git commit -m "init sub"
+	)
+	git submodule add "/å äö" &&
+	test -n "$(git submodule | grep "å äö")"
+'
 test_done