Improve the discussion of the absolute-filter alternative.

support/mnt-excl

@@ -18,11 +18,13 @@
 # easily adapted to read /etc/mtab or similar.
 #
 # ADDENDUM:  The addition of the --filter option (which has support for
-# absolute-anchored excludes) has made this script less useful than it
-# was.  Beginning with 2.6.4, you can achieve the effect of this script
-# through this command:
+# absolute-anchored excludes) can make this screen unneeded in some
+# scenarios.  If you don't need delete protection on the receiving side
+# (or if the destination path is identical to the source path), then you
+# can exclude some absolute paths from the transfer based on the mount
+# dirs.  For instance:
 #
-# awk '{print $2}' /proc/mounts | rsync -f 'merge,/- -' host:/dir /dest/
+# awk '{print $2}' /proc/mounts | rsync -avf 'merge,/- -' /dir host:/dest/
 
 use strict;
 use warnings;