diff: honor binariness specified in attributes

The code shuffling mistakenly lost binariness specified with the
attribute mecahnism and made it always guess from the data.

Noticed by Johannes, with two test cases to t4020.

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

1 files changed, 12 insertions, 0 deletions

diff --git a/t/t4020-diff-external.sh b/t/t4020-diff-external.sh
index f0045cd788..ed3bd5b3fe 100755
--- a/t/t4020-diff-external.sh
+++ b/t/t4020-diff-external.sh
@@ -94,4 +94,16 @@ test_expect_success 'diff attribute should apply only to diff' '
 
 '
 
+test_expect_success 'no diff with -diff' '
+	echo >.gitattributes "file -diff" &&
+	git diff | grep Binary
+'
+
+echo NULZbetweenZwords | tr Z '\0' > file
+
+test_expect_success 'force diff with "diff"' '
+	echo >.gitattributes "file diff" &&
+	git diff | grep -a second
+'
+
 test_done