mingw: verify that paths are not mistaken for remote nicknames

This added test case simply verifies that users will not be bothered
with bogus complaints à la

	warning: unable to access '.git/remotes/D:\repo': Invalid argument

when fetching from a Windows path (in this case, D:\repo).

[j6t: mark the new test as test_expect_failure]

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5580-clone-push-unc.sh

@@ -1,10 +1,10 @@
 #!/bin/sh
 
-test_description='various UNC path tests (Windows-only)'
+test_description='various Windows-only path tests'
 . ./test-lib.sh
 
 if ! test_have_prereq MINGW; then
-	skip_all='skipping UNC path tests, requires Windows'
+	skip_all='skipping Windows-only path tests'
 	test_done
 fi
 
@@ -45,4 +45,10 @@ test_expect_success push '
 	test "$rev" = "$(git rev-parse --verify refs/heads/to-push)"
 '
 
+test_expect_failure 'remote nick cannot contain backslashes' '
+	BACKSLASHED="$(pwd | tr / \\\\)" &&
+	git ls-remote "$BACKSLASHED" >out 2>err &&
+	test_i18ngrep ! "unable to access" err
+'
+
 test_done