Prevent example command from overflowing margins

docs/using.rst

@@ -127,7 +127,8 @@ potentially be a separate directory for each domain. When requested a
 certificate for multiple domains, each domain will use the most recently
 specified ``--webroot-path``.  So, for instance,
 
-``letsencrypt certonly --webroot -w /var/www/example/ -d www.example.com -d example.com -w /var/www/other -d other.example.net -d another.other.example.net``
+``letsencrypt certonly --webroot -w /var/www/example/ -d www.example.com -d``
+``example.com -w /var/www/eg -d other.example.net -d m.other.example.net``
 
 would obtain a single certificate for all of those names, using the
 ``/var/www/example`` webroot directory for the first two, and