t/t4016-diff-quote: change from skip_all=* to prereq skip

Change this test to skip test with test prerequisites, and to do setup
work in tests. This improves the skipped statistics on platforms where
the test isn't run.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4016-diff-quote.sh

@@ -13,12 +13,14 @@ P1='pathname	with HT'
 P2='pathname with SP'
 P3='pathname
 with LF'
-: 2>/dev/null >"$P1" && test -f "$P1" && rm -f "$P1" || {
-	skip_all='Your filesystem does not allow tabs in filenames, test skipped.'
-	test_done
-}
+if : 2>/dev/null >"$P1" && test -f "$P1" && rm -f "$P1"
+then
+	test_set_prereq TABS_IN_FILENAMES
+else
+	say 'Your filesystem does not allow tabs in filenames'
+fi
 
-test_expect_success setup '
+test_expect_success TABS_IN_FILENAMES setup '
 	echo P0.0 >"$P0.0" &&
 	echo P0.1 >"$P0.1" &&
 	echo P0.2 >"$P0.2" &&
@@ -38,6 +40,7 @@ test_expect_success setup '
 	:
 '
 
+test_expect_success TABS_IN_FILENAMES 'setup expected files' '
 cat >expect <<\EOF
  rename pathname.1 => "Rpathname\twith HT.0" (100%)
  rename pathname.3 => "Rpathname\nwith LF.0" (100%)
@@ -47,11 +50,14 @@ cat >expect <<\EOF
  rename pathname.0 => Rpathname.0 (100%)
  rename "pathname\twith HT.0" => Rpathname.1 (100%)
 EOF
-test_expect_success 'git diff --summary -M HEAD' '
+'
+
+test_expect_success TABS_IN_FILENAMES 'git diff --summary -M HEAD' '
 	git diff --summary -M HEAD >actual &&
 	test_cmp expect actual
 '
 
+test_expect_success TABS_IN_FILENAMES 'setup expected files' '
 cat >expect <<\EOF
  pathname.1 => "Rpathname\twith HT.0"            |    0
  pathname.3 => "Rpathname\nwith LF.0"            |    0
@@ -62,7 +68,9 @@ cat >expect <<\EOF
  "pathname\twith HT.0" => Rpathname.1            |    0
  7 files changed, 0 insertions(+), 0 deletions(-)
 EOF
-test_expect_success 'git diff --stat -M HEAD' '
+'
+
+test_expect_success TABS_IN_FILENAMES 'git diff --stat -M HEAD' '
 	git diff --stat -M HEAD >actual &&
 	test_cmp expect actual
 '