Adding information about IPYTHONDIR to usage of ipcluster and friends.

IPython/kernel/scripts/ipcluster.py

@@ -736,8 +736,11 b' def get_args():'
     
     parser = argparse.ArgumentParser(
         description='IPython cluster startup.  This starts a controller and\
-        engines using various approaches.  THIS IS A TECHNOLOGY PREVIEW AND\
-        THE API WILL CHANGE SIGNIFICANTLY BEFORE THE FINAL RELEASE.'
+        engines using various approaches.  Use the IPYTHONDIR environment\
+        variable to change your IPython directory from the default of\
+        .ipython or _ipython.  The log and security subdirectories of your\
+        IPython directory will be used by this script for log files and\
+        security files.'
     )
     subparsers = parser.add_subparsers(
         help='available cluster types.  For help, do "ipcluster TYPE --help"')

IPython/kernel/scripts/ipcontroller.py

@@ -264,7 +264,14 b' def init_config():'
     Initialize the configuration using default and command line options.
     """
     
-    parser = OptionParser()
+    parser = OptionParser("""ipcontroller [options]
+
+Start an IPython controller.
+
+Use the IPYTHONDIR environment variable to change your IPython directory 
+from the default of .ipython or _ipython.  The log and security 
+subdirectories of your IPython directory will be used by this script 
+for log files and security files.""")
     
     # Client related options
     parser.add_option(

IPython/kernel/scripts/ipengine.py

@@ -140,7 +140,14 b' def init_config():'
     Initialize the configuration using default and command line options.
     """
     
-    parser = OptionParser()
+    parser = OptionParser("""ipengine [options]
+
+Start an IPython engine.
+
+Use the IPYTHONDIR environment variable to change your IPython directory 
+from the default of .ipython or _ipython.  The log and security 
+subdirectories of your IPython directory will be used by this script 
+for log files and security files.""")
     
     parser.add_option(
         "--furl-file",