added a little pointer for cloning clean copies

README

@@ -207,7 +207,10 @@ clone [may require Internet access]
   Compare ~/another/testing and ~/another/more_testing. They should be
   identical! Here we've illustrated the ability to specify a destination
   directory for *clone*. If unspecified, the repo name of our source will
-  be the name of the destination.
+  be the name of the destination. This is especially useful when you want
+  to make sure that the repository you just pushed to actually contains
+  what you think, since you can have a second (clean) copy in another
+  directory (see "pull", below).
 
   Here, we've cloned a repo in a local directory. This is of limited usefulness,
   since generally you're going to want to clone repos stored on other machines.