t4014: make output-directory tests self-contained

As noted by Gábor in [1], the new tests in edefc31 ("format-patch:
create leading components of output directory", 2019-10-11) cannot be
run independently. Fix this.

[1] https://public-inbox.org/git/20191011144650.GM29845@szeder.dev/

Signed-off-by: Bert Wesarg <bert.wesarg@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: bertwesarg

t/t4014-format-patch.sh

@@ -1615,17 +1615,20 @@ test_expect_success 'format-patch -o with no leading directories' '
 '
 
 test_expect_success 'format-patch -o with leading existing directories' '
-	git format-patch -o patches/side master..side &&
+	rm -rf existing-dir &&
+	mkdir existing-dir &&
+	git format-patch -o existing-dir/patches master..side &&
 	count=$(git rev-list --count master..side) &&
-	ls patches/side >list &&
+	ls existing-dir/patches >list &&
 	test_line_count = $count list
 '
 
 test_expect_success 'format-patch -o with leading non-existing directories' '
-	rm -fr patches &&
-	git format-patch -o patches/side master..side &&
+	rm -rf non-existing-dir &&
+	git format-patch -o non-existing-dir/patches master..side &&
 	count=$(git rev-list --count master..side) &&
-	ls patches/side >list &&
+	test_path_is_dir non-existing-dir &&
+	ls non-existing-dir/patches >list &&
 	test_line_count = $count list
 '