t7400: test of UTF-8 submodule names pass under Mac OS

submodules with names using UTF-8 need core.precomposeunicode true
under Mac OS X, set it in the test case.

Improve the portability:

  - Not all shells on all OS may understand literal UTF-8 strings.
  - Use a help variable filled by printf, as we do it in e.g. t0050.

"strange names" can be called UTF-8, rephrase the heading.

While at it, unbreak &&-chain in the test, and use test_config.

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7400-submodule-basic.sh

@@ -868,16 +868,19 @@ 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" &&
+test_expect_success 'submodule with UTF-8 name' '
+	svname=$(printf "\303\245 \303\244\303\266") &&
+	mkdir "$svname" &&
 	(
-		cd "å äö" &&
+		cd "$svname" &&
 		git init &&
-		touch sub
-		git add sub
+		>sub &&
+		git add sub &&
 		git commit -m "init sub"
-	)
-	git submodule add "/å äö" &&
-	test -n "$(git submodule | grep "å äö")"
+	) &&
+	test_config core.precomposeunicode true &&
+	git submodule add ./"$svname" &&
+	git submodule >&2 &&
+	test -n "$(git submodule | grep "$svname")"
 '
 test_done