Add a basic tutorial for the tools in depot_tools.

git_common.py

 # Copyright 2014 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.
 
 # Monkeypatch IMapIterator so that Ctrl-C can kill everything properly.
 # Derived from https://gist.github.com/aljungberg/626518
 import multiprocessing.pool
 from multiprocessing.pool import IMapIterator
 def wrapper(func):
   def wrap(self, timeout=None):
@@ skipping 455 matching lines @@
 
 
 def run_stream(*cmd, **kwargs):
   """Runs a git command. Returns stdout as a PIPE (file-like object).
 
   stderr is dropped to avoid races if the process outputs to both stdout and
   stderr.
   """
   kwargs.setdefault('stderr', subprocess2.VOID)
   kwargs.setdefault('stdout', subprocess2.PIPE)
-  cmd = (GIT_EXE,) + cmd
+  cmd = (GIT_EXE, '-c', 'color.ui=never') + cmd
   proc = subprocess2.Popen(cmd, **kwargs)
   return proc.stdout
 
 
 def run_with_stderr(*cmd, **kwargs):
   """Runs a git command.
 
   Returns (stdout, stderr) as a pair of strings.
 
   kwargs
     autostrip (bool) - Strip the output. Defaults to True.
     indata (str) - Specifies stdin data for the process.
   """
   kwargs.setdefault('stdin', subprocess2.PIPE)
   kwargs.setdefault('stdout', subprocess2.PIPE)
   kwargs.setdefault('stderr', subprocess2.PIPE)
   autostrip = kwargs.pop('autostrip', True)
   indata = kwargs.pop('indata', None)
 
-  cmd = (GIT_EXE,) + cmd
+  cmd = (GIT_EXE, '-c', 'color.ui=never') + cmd
   proc = subprocess2.Popen(cmd, **kwargs)
   ret, err = proc.communicate(indata)
   retcode = proc.wait()
   if retcode != 0:
     raise subprocess2.CalledProcessError(retcode, cmd, os.getcwd(), ret, err)
 
   if autostrip:
     ret = (ret or '').strip()
     err = (err or '').strip()
 
@@ skipping 122 matching lines @@
     return None
   return ret
 
 
 def upstream(branch):
   try:
     return run('rev-parse', '--abbrev-ref', '--symbolic-full-name',
                branch+'@{upstream}')
   except subprocess2.CalledProcessError:
     return None