Hey you forgot the patch!
+From nobody Mon Sep 17 00:00:00 2001
+From: A U Thor <a.u.thor@example.com>
+Date: Mon, 17 Sep 2001 00:00:00 +0900
+Mime-Version: 1.0
+Content-Type: Text/Plain; charset=us-ascii
+Content-Transfer-Encoding: Quoted-Printable
+
+=0A=0AFrom: F U Bar <f.u.bar@example.com>
+Subject: [PATCH] updates=0A=0AThis is to fix diff-format documentation.
+
+diff --git a/Documentation/diff-format.txt b/Documentation/diff-format.txt
+index b426a14..97756ec 100644
+--- a/Documentation/diff-format.txt
++++ b/Documentation/diff-format.txt
+@@ -81,7 +81,7 @@ The "diff" formatting options can be customized via the
+ environment variable 'GIT_DIFF_OPTS'. For example, if you
+ prefer context diff:
+=20
+- GIT_DIFF_OPTS=3D-c git-diff-index -p $(cat .git/HEAD)
++ GIT_DIFF_OPTS=3D-c git-diff-index -p HEAD
+=20
+=20
+ 2. When the environment variable 'GIT_EXTERNAL_DIFF' is set, the