Add an example refuse file.

PR:		17972
Submitted by:	Michael Lucas <mwlucas@blackhelicopters.org>

share/examples/cvsup/README

@@ -39,3 +39,8 @@ you will need to edit in an appropriate "host" setting.  See:
     http://www.freebsd.org/handbook/mirrors.html
 
 for an up-to-date list of public CVSup mirror sites.
+
+To prevent CVSup from updating particular directories and files, use
+this file:
+
+    refuse

share/examples/cvsup/refuse

@@ -0,0 +1,29 @@
+# $FreeBSD$
+#
+#This is an example "refuse file".  CVSup will not touch anything listed
+#in the refuse file.
+#
+#You can copy this file to your sup directory and uncomment or add
+#whatever you would like.  If you are using the default setting for the
+#CVSup "base" directory, your sup directory is /usr/sup.  If you have
+#changed your base directory, your sup directory is /path/to/base/sup.
+#
+#Use this example if you have modified /usr/src/etc/sendmail/freebsd.mc
+#to reflect your local configuration, and you do not want CVSup to
+#overwrite it:
+#
+#etc/sendmail/freebsd.mc
+#
+#If you list a directory, changes to any files beneath that directory
+#will be rejected.  For example, if you are an English speaker and are
+#not tracking the foreign-language ports, you can uncomment the following.
+#
+#ports/chinese
+#ports/german
+#ports/japanese
+#ports/korean
+#ports/russian
+#ports/vietnamese
+#
+#Use this feature with care -- many parts of the src distribution depend
+#on files in completely different parts.