patchdiff: treat -crlf files as binary

diff --git a/diff.c b/diff.c
index 18fa7a7..258b438 100644
--- a/diff.c
+++ b/diff.c
@@ -1314,36 +1314,46 @@ static void emit_binary_diff(FILE *file, mmfile_t *one, mmfile_t *two)
 static void setup_diff_attr_check(struct git_attr_check *check)
 {
 	static struct git_attr *attr_diff;
+	static struct git_attr *attr_crlf;
 
-	if (!attr_diff) {
+	if (!attr_diff)
 		attr_diff = git_attr("diff", 4);
-	}
+	if (!attr_crlf)
+		attr_crlf = git_attr("crlf", 4);
 	check[0].attr = attr_diff;
+	check[1].attr = attr_crlf;
 }
 
 static void diff_filespec_check_attr(struct diff_filespec *one)
 {
-	struct git_attr_check attr_diff_check;
+	struct git_attr_check attr_diff_check[2];
 	int check_from_data = 0;
 
 	if (one->checked_attr)
 		return;
 
-	setup_diff_attr_check(&attr_diff_check);
+	setup_diff_attr_check(attr_diff_check);
 	one->is_binary = 0;
 	one->funcname_pattern_ident = NULL;
 
-	if (!git_checkattr(one->path, 1, &attr_diff_check)) {
+	if (!git_checkattr(one->path, 2, attr_diff_check)) {
 		const char *value;
 
-		/* binaryness */
-		value = attr_diff_check.value;
+		/* binaryness; check both "diff" and "crlf" */
+		value = attr_diff_check[0].value;
 		if (ATTR_TRUE(value))
 			;
 		else if (ATTR_FALSE(value))
 			one->is_binary = 1;
-		else
-			check_from_data = 1;
+		else {
+			const char *crlf = attr_diff_check[1].value;
+			if (ATTR_TRUE(crlf))
+				;
+			else if (ATTR_FALSE(crlf))
+				one->is_binary = 1;
+			else
+				check_from_data = 1;
+		}
 
 		/* funcname pattern ident */
 		if (ATTR_TRUE(value) || ATTR_FALSE(value) || ATTR_UNSET(value))

diff --git i/Documentation/gitattributes.txt w/Documentation/gitattributes.txt
index db16b0c..ec8a860 100644
--- i/Documentation/gitattributes.txt
+++ w/Documentation/gitattributes.txt
@@ -105,9 +105,8 @@ Set::
 
 Unset::
 
-	Unsetting the `crlf` attribute on a path is meant to
-	mark the path as a "binary" file.  The path never goes
-	through line endings conversion upon checkin/checkout.
+	Unsetting the `crlf` attribute on a path is tells git
+	not to attempt any end-of-line conversion  upon checkin/checkout.
 
 Unspecified::
 
@@ -482,6 +481,40 @@ in the file.  E.g. the string `$Format:%H$` will be replaced by the
 commit hash.
 
 
+USING ATTRIBUTE MACROS
+----------------------
+
+You do not want any end-of-line conversions applied to, nor textual diffs
+produced for any binary file you track.  You would need to specify e.g.
+
+------------
+*.jpg -crlf -diff
+------------
+
+but that is cumbersome.  Using attribute macros, you can specify groups of
+attributes set or unset at the same time.  The system knows a built-in
+attribute macro, `binary`:
+
+------------
+*.jpg binary
+------------
+
+which is equivalent to the above.  Note that the attribute macros can only
+be "Set" (see the above example).
+
+
+DEFINING ATTRIBUTE MACROS
+-------------------------
+
+Custom attribute macros can be defined only in the `.gitattributes` file
+at the toplevel (i.e. not in any subdirectory).  The built-in attribute
+macro "binary" is equivalent to:
+
+------------
+[attr]binary -diff -crlf
+------------
+
+
 EXAMPLE
 -------