Make gclient sync use cpu count for default jobs

gclient.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.
 
 """Meta checkout manager supporting both Subversion and GIT.
 
 Files
   .gclient      : Current client configuration, written by 'config' command.
                   Format is a Python script defining 'solutions', a list whose
@@ skipping 1523 matching lines @@
   parser.epilog = getattr(obj, 'epilog', None)
 
 
 def Parser():
   """Returns the default parser."""
   parser = optparse.OptionParser(version='%prog ' + __version__)
   # some arm boards have issues with parallel sync.
   if platform.machine().startswith('arm'):
     jobs = 1
   else:
-    jobs = 8
+    jobs = max(8, gclient_utils.NumLocalCpus())
   gclientfile_default = os.environ.get('GCLIENT_FILE', '.gclient')
   parser.add_option('-j', '--jobs', default=jobs, type='int',
                     help='Specify how many SCM commands can run in parallel; '
-                          'default=%default')
+                          'defaults to number of cpu cores (%default)')
   parser.add_option('-v', '--verbose', action='count', default=0,
                     help='Produces additional output for diagnostics. Can be '
                           'used up to three times for more logging info.')
   parser.add_option('--gclientfile', dest='config_filename',
                     default=None,
                     help='Specify an alternate %s file' % gclientfile_default)
   parser.add_option('--spec',
                     default=None,
                     help='create a gclient file containing the provided '
                          'string. Due to Cygwin/Python brokenness, it '
@@ skipping 74 matching lines @@
   except (gclient_utils.Error, subprocess2.CalledProcessError), e:
     print >> sys.stderr, 'Error: %s' % str(e)
     return 1
 
 
 if '__main__' == __name__:
   fix_encoding.fix_encoding()
   sys.exit(Main(sys.argv[1:]))
 
 # vim: ts=2:sw=2:tw=80:et: