test-lib: provide UTF8 behaviour as a prerequisite

UTF8 behaviour of the filesystem (conversion from nfd to nfc)  plays a
role in several tests and is tested in several tests. Therefore, move
the test from t0050 into the test lib and use the prerequisite in t0050.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/README

@@ -629,6 +629,11 @@ use these, and "test_set_prereq" for how to define your own.
 
    Test is run on a case insensitive file system.
 
+ - UTF8_NFD_TO_NFC
+
+   Test is run on a filesystem which converts decomposed utf-8 (nfd)
+   to precomposed utf-8 (nfc).
+
 Tips for Writing Tests
 ----------------------
 

t/t0050-filesystem.sh

@@ -7,22 +7,6 @@ test_description='Various filesystem issues'
 auml=$(printf '\303\244')
 aumlcdiar=$(printf '\141\314\210')
 
-unibad=
-test_expect_success 'see what we expect' '
-
-	test_unicode=test_expect_success &&
-	mkdir junk &&
-	>junk/"$auml" &&
-	case "$(cd junk && echo *)" in
-	"$aumlcdiar")
-		test_unicode=test_expect_failure &&
-		unibad=t
-		;;
-	*)	;;
-	esac &&
-	rm -fr junk
-'
-
 if test_have_prereq CASE_INSENSITIVE_FS
 then
 	say "will test on a case insensitive filesystem"
@@ -31,8 +15,14 @@ else
 	test_case=test_expect_success
 fi
 
-test "$unibad" &&
+if test_have_prereq UTF8_NFD_TO_NFC
+then
 	say "will test on a unicode corrupting filesystem"
+	test_unicode=test_expect_failure
+else
+	test_unicode=test_expect_success
+fi
+
 test_have_prereq SYMLINKS ||
 	say "will test on a filesystem lacking symbolic links"
 

t/test-lib.sh

@@ -670,6 +670,19 @@ test_lazy_prereq CASE_INSENSITIVE_FS '
 	test "$(cat CamelCase)" != good
 '
 
+test_lazy_prereq UTF8_NFD_TO_NFC '
+	# check whether FS converts nfd unicode to nfc
+	auml=$(printf "\303\244")
+	aumlcdiar=$(printf "\141\314\210")
+	>"$auml" &&
+	case "$(echo *)" in
+	"$aumlcdiar")
+		true ;;
+	*)
+		false ;;
+	esac
+'
+
 # When the tests are run as root, permission tests will report that
 # things are writable when they shouldn't be.
 test -w / || test_set_prereq SANITY