t4126: fix "funny directory name" test on Windows (again)

Even though "git update-index --cacheinfo" ought to be filesystem
agnostic,

    $ git update-index --add --cacheinfo "100644,$empty_blob,funny /empty"

fails only on Windows, and this unfortunately makes the approach of
the previous step unworkable.

Resurrect the earlier approach to give up on running the test on
known-bad platforms.  Instead of computing a custom prerequisite,
just use !MINGW we have used elsewhere.

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

t/t4126-apply-empty.sh

@@ -66,29 +66,28 @@ test_expect_success 'apply --index create' '
 	git diff --exit-code
 '
 
-test_expect_success 'parsing a patch with no-contents and a funny pathname' '
+test_expect_success !MINGW 'apply with no-contents and a funny pathname' '
+	test_when_finished "rm -fr \"funny \"; git reset --hard" &&
+
+	mkdir "funny " &&
+	>"funny /empty" &&
+	git add "funny /empty" &&
+	git diff HEAD -- "funny /" >sample.patch &&
+	git diff -R HEAD -- "funny /" >elpmas.patch &&
+
 	git reset --hard &&
-	empty_blob=$(test_oid empty_blob) &&
-	echo "$empty_blob" >expect &&
 
-	git update-index --add --cacheinfo "100644,$empty_blob,funny /empty" &&
-	git diff --cached HEAD -- "funny /" >sample.patch &&
-	git diff --cached -R HEAD -- "funny /" >elpmas.patch &&
-	git reset &&
+	git apply --stat --check --apply sample.patch &&
+	test_must_be_empty "funny /empty" &&
 
-	git apply --cached --stat --check --apply sample.patch &&
-	git rev-parse --verify ":funny /empty" >actual &&
-	test_cmp expect actual &&
+	git apply --stat --check --apply elpmas.patch &&
+	test_path_is_missing "funny /empty" &&
 
-	git apply --cached --stat --check --apply elpmas.patch &&
-	test_must_fail git rev-parse --verify ":funny /empty" &&
+	git apply -R --stat --check --apply elpmas.patch &&
+	test_must_be_empty "funny /empty" &&
 
-	git apply -R --cached --stat --check --apply elpmas.patch &&
-	git rev-parse --verify ":funny /empty" >actual &&
-	test_cmp expect actual &&
-
-	git apply -R --cached --stat --check --apply sample.patch &&
-	test_must_fail git rev-parse --verify ":funny /empty"
+	git apply -R --stat --check --apply sample.patch &&
+	test_path_is_missing "funny /empty"
 '
 
 test_done