[PATCH] Make attributes "-diff" and "diff" work as advertized

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

In Documentation/gitattributes.txt, it says that you can suppress
diffs by setting the attribute "-diff", and you can override the
binary detection with the attribute "diff".

Make it work.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---

	Evidently, this is on top of "next" + the funcname patches, since
	I realized it only when working on top of them.

	However, it should also apply cleanly to "master", and even 
	"maint". (The only reason I'm not doing it right now, is that I am 
	in the middle of preparing a patch pair, and doing this patch was 
	easy enough with rebase -i.)

 diff.c                   |   15 +++++++--------
 t/t4020-diff-external.sh |   12 ++++++++++++
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/diff.c b/diff.c
index 21e61af..e92db5c 100644
--- a/diff.c
+++ b/diff.c
@@ -1170,13 +1170,19 @@ static void diff_filespec_check_attr(struct diff_filespec *one)
 	one->is_binary = 0;
 	one->funcname_pattern_ident = NULL;
 
+	if (!one->data && DIFF_FILE_VALID(one))
+		diff_populate_filespec(one, 0);
+
+	if (one->data)
+		one->is_binary = buffer_is_binary(one->data, one->size);
+
 	if (!git_checkattr(one->path, 1, &attr_diff_check)) {
 		const char *value;
 
 		/* binaryness */
 		value = attr_diff_check.value;
 		if (ATTR_TRUE(value))
-			;
+			one->is_binary = 0;
 		else if (ATTR_FALSE(value))
 			one->is_binary = 1;
 
@@ -1186,13 +1192,6 @@ static void diff_filespec_check_attr(struct diff_filespec *one)
 		else
 			one->funcname_pattern_ident = value;
 	}
-
-	if (!one->data && DIFF_FILE_VALID(one))
-		diff_populate_filespec(one, 0);
-
-	if (one->data)
-		one->is_binary = buffer_is_binary(one->data, one->size);
-
 }
 
 int diff_filespec_is_binary(struct diff_filespec *one)
diff --git a/t/t4020-diff-external.sh b/t/t4020-diff-external.sh
index f0045cd..ed3bd5b 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
-- 
1.5.3.rc0.2712.g125b7f