Add -f option for reading hosts from file or stdin.

docs/man/man1/cdist.text

@@ -14,7 +14,7 @@ cdist [-h] [-d] [-v] [-V] {banner,config,shell} ...
 
 cdist banner [-h] [-d] [-v]
 
-cdist config [-h] [-d] [-V] [-c CONF_DIR] [-i MANIFEST] [-p] [-s] host [host ...]
+cdist config [-h] [-d] [-V] [-c CONF_DIR] [-f HOSTFILE] [-i MANIFEST] [-p] [-s] [host [host ...]]
 
 cdist shell [-h] [-d] [-v] [-s SHELL]
 
@@ -63,6 +63,11 @@ Configure one or more hosts
     --conf-dir argument have higher precedence over those set through the
     environment variable.
 
+-f HOSTFILE, --file HOSTFILE::
+    Read hosts to operate on from specified file or from stdin if '-'
+    (each host on separate line). If no host or host file is
+    specified then, by default, read hosts from stdin.
+
 -i MANIFEST, --initial-manifest MANIFEST::
     Path to a cdist manifest or - to read from stdin
 
@@ -105,6 +110,9 @@ EXAMPLES
     --remote-copy /path/to/my/remote/copy \
     -p ikq02.ethz.ch ikq03.ethz.ch ikq04.ethz.ch
 
+# Configure hosts in parallel by reading hosts from file loadbalancers
+% cdist config -f loadbalancers
+
 # Display banner
 cdist banner