Try to clarify "gcl help try" some.

trychange.py

 #!/usr/bin/python
 # Copyright (c) 2009 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 """Client-side script to send a try job to the try server. It communicates to
 the try server by either writting to a svn repository or by directly connecting
 to the server by HTTP.
 """
 
 
@@ skipping 14 matching lines @@
 import gclient
 import gclient_scm
 import presubmit_support
 import upload
 
 __version__ = '1.1.1'
 
 
 # Constants
 HELP_STRING = "Sorry, Tryserver is not available."
-USAGE = r"""%prog [options]
+USAGE = r"""%prog [change_name] [options]
 
 Client-side script to send a try job to the try server. It communicates to
 the try server by either writting to a svn repository or by directly connecting
 to the server by HTTP.
 
 
 Examples:
+  Try a change against a particular revision:
+    %prog change_name -r 123
+
   A git patch off a web site (git inserts a/ and b/) and fix the base dir:
     %prog --url http://url/to/patch.diff --patchlevel 1 --root src
 
   Use svn to store the try job, specify an alternate email address and use a
   premade diff file on the local drive:
     %prog --email user@example.com
             --svn_repo svn://svn.chromium.org/chrome-try/try --diff foo.diff
 
-  Running only on a 'mac' slave with revision src@123 and clobber first; specify
+  Running only on a 'mac' slave with revision 123 and clobber first; specify
   manually the 3 source files to use for the try job:
-    %prog --bot mac --revision src@123 --clobber -f src/a.cc -f src/a.h
+    %prog --bot mac --revision 123 --clobber -f src/a.cc -f src/a.h
             -f include/b.h
 
 """
 
 class InvalidScript(Exception):
   def __str__(self):
     return self.args[0] + '\n' + HELP_STRING
 
 
 class NoTryServerAccess(Exception):
@@ skipping 522 matching lines @@
     if patch_name == 'Unnamed':
       print "Note: use --name NAME to change the try's name."
   except (InvalidScript, NoTryServerAccess), e:
     if swallow_exception:
       return
     print e
 
 
 if __name__ == "__main__":
   TryChange(None, None, False)