Make git cl smarter about subcommands typos.

git_cl.py

 #!/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.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld."""
 
+import difflib
 import json
 import logging
 import optparse
 import os
 import re
 import stat
 import sys
 import textwrap
+import urllib2
 import urlparse
-import urllib2
 
 try:
   import readline  # pylint: disable=F0401,W0611
 except ImportError:
   pass
 
 
 from third_party import colorama
 from third_party import upload
 import breakpad  # pylint: disable=W0611
@@ skipping 1982 matching lines @@
     cfd_path = os.path.join('/usr', 'lib', 'clang-format',
                             'clang-format-diff.py')
     if not os.path.exists(cfd_path):
       DieWithError('Could not find clang-format-diff at %s.' % cfd_path)
     cmd = [sys.executable, cfd_path, '-style', 'Chromium']
     RunCommand(cmd, stdin=diff_output)
 
   return 0
 
 
+### Glue code for subcommand handling.
+
+
+def Commands():
+  """Returns a dict of command and their handling function."""
+  module = sys.modules[__name__]
+  cmds = (fn[3:] for fn in dir(module) if fn.startswith('CMD'))
+  return dict((cmd, getattr(module, 'CMD' + cmd)) for cmd in cmds)
+
+
 def Command(name):
-  return getattr(sys.modules[__name__], 'CMD' + name, None)
+  """Retrieves the function to handle a command."""
+  commands = Commands()
+  if name in commands:
+    return commands[name]
+
+  # Try to be smart and look if there's something similar.
+  commands_with_prefix = [c for c in commands if c.startswith(name)]
+  if len(commands_with_prefix) == 1:
+    return commands[commands_with_prefix[0]]
+
+  # A #closeenough approximation of levenshtein distance.
+  def close_enough(a, b):
+    return difflib.SequenceMatcher(a=a, b=b).ratio()
+
+  hamming_commands = sorted(
+      ((close_enough(c, name), c) for c in commands),
+      reverse=True)
+  if (hamming_commands[0][0] - hamming_commands[1][0]) < 0.3:
+    # Too ambiguous.
+    return
+
+  if hamming_commands[0][0] < 0.8:
+    # Not similar enough. Don't be a fool and run a random command.
+    return
+
+  return commands[hamming_commands[0][1]]
 
 
 def CMDhelp(parser, args):
   """print list of commands or help for a specific command"""
   _, args = parser.parse_args(args)
   if len(args) == 1:
     return main(args + ['--help'])
   parser.print_help()
   return 0
 
 
 def GenUsage(parser, command):
   """Modify an OptParse object with the function's documentation."""
   obj = Command(command)
+  # Get back the real command name in case Command() guess the actual command
+  # name.
+  command = obj.__name__[3:]
   more = getattr(obj, 'usage_more', '')
   if command == 'help':
     command = '<command>'
   else:
     # OptParser.description prefer nicely non-formatted strings.
     parser.description = re.sub('[\r\n ]{2,}', ' ', obj.__doc__)
   parser.set_usage('usage: %%prog %s [options] %s' % (command, more))
 
 
 def main(argv):
   """Doesn't parse the arguments here, just find the right subcommand to
   execute."""
   if sys.hexversion < 0x02060000:
     print >> sys.stderr, (
         '\nYour python version %s is unsupported, please upgrade.\n' %
         sys.version.split(' ', 1)[0])
     return 2
 
   # Reload settings.
   global settings
   settings = Settings()
 
   # Do it late so all commands are listed.
-  CMDhelp.usage_more = ('\n\nCommands are:\n' + '\n'.join([
-      '  %-10s %s' % (fn[3:], Command(fn[3:]).__doc__.split('\n')[0].strip())
-      for fn in dir(sys.modules[__name__]) if fn.startswith('CMD')]))
+  commands = Commands()
+  length = max(len(c) for c in commands)
+  docs = sorted(
+      (name, handler.__doc__.split('\n')[0].strip())
+      for name, handler in commands.iteritems())
+  CMDhelp.usage_more = ('\n\nCommands are:\n' + '\n'.join(
+      '  %-*s %s' % (length, name, doc) for name, doc in docs))
 
   # Create the option parse and add --verbose support.
   parser = optparse.OptionParser()
   parser.add_option(
       '-v', '--verbose', action='count', default=0,
       help='Use 2 times for more debugging info')
   old_parser_args = parser.parse_args
   def Parse(args):
     options, args = old_parser_args(args)
     if options.verbose >= 2:
@@ skipping 23 matching lines @@
   GenUsage(parser, 'help')
   return CMDhelp(parser, argv)
 
 
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   colorama.init()
   sys.exit(main(sys.argv[1:]))