Add --help support to git-tree-prune.

git-utils/git-tree-prune

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
-"""A tool for listing branches with closed and abandoned issues."""
+"""Lists branches with closed and abandoned issues."""
 
+import optparse
 import os
 import sys
 import urllib2
 
 BASE_DIR = os.path.dirname(os.path.abspath(__file__))
 DEPOT_TOOLS_DIR = os.path.dirname(BASE_DIR)
 sys.path.insert(0, DEPOT_TOOLS_DIR)
 
 import git_cl
 
 
 def get_branches():
   """Get list of all local git branches."""
   return [Branch(l[2:]) for l in git_cl.RunGit(["branch"]).splitlines()]
 
 
 class Branch(git_cl.Changelist):
   def __init__(self, name):
     git_cl.Changelist.__init__(self, branchref=name)
     self._issue_status = None
-    
+
   def GetStatus(self):
     if not self._issue_status:
       if self.GetIssue():
-        try:        
+        try:
           issue_properties = self.RpcServer().get_issue_properties(
               self.GetIssue(), None)
           if issue_properties['closed']:
             self._issue_status = 'closed'
           else:
             self._issue_status = 'pending'
         except urllib2.HTTPError, e:
           if e.code == 404:
             self._issue_status = 'abandoned'
       else:
         self._issue_status = 'no-issue'
     return self._issue_status
 
 
-def main(argv):
+def main():
+  parser = optparse.OptionParser(usage=sys.modules['__main__'].__doc__)
+  options, args = parser.parse_args()
+  if args:
+    parser.error('Unsupported arg: %s' % args)
+
   branches = get_branches()
   filtered = { 'closed' : [],
                'pending' : [],
                'abandoned' : [],
                'no-issue' : []}
 
   for branch in branches:
     filtered[branch.GetStatus()].append(branch)
 
   print "# Branches with closed issues"
@@ skipping 11 matching lines @@
         branch.GetBranch(), branch.GetIssue())
 
   print "\n# Branches without associated issues"
   for branch in filtered['no-issue']:
     print "# Branch %s" % (branch.GetBranch())
 
   return 0
 
 
 if __name__ == '__main__':
-  sys.exit(main(sys.argv[1:]))
+  sys.exit(main())