Extract git version check code from gclient_scm.py into scm.py where it belongs.

scm.py

 # Copyright (c) 2006-2009 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.
 
 """SCM-specific utility classes."""
 
 import glob
 import os
 import re
 import shutil
@@ skipping 252 matching lines @@
     short_sha = GIT.Capture(['rev-parse', '--short=4', 'HEAD'], cwd)[0].strip()
     return "%s-%s" % (GIT.GetBranch(cwd), short_sha)
 
   @staticmethod
   def GetCheckoutRoot(path):
     """Returns the top level directory of a git checkout as an absolute path.
     """
     root = GIT.Capture(['rev-parse', '--show-cdup'], path)[0].strip()
     return os.path.abspath(os.path.join(path, root))
 
+  @staticmethod
+  def AssertVersion(min_version):
+    """Asserts git's version is at least min_version."""
+    def only_int(val):
+      if val.isdigit():
+        return int(val)
+      else:
+        return 0
+    current_version =  GIT.Capture(['--version'])[0].split()[-1]
+    current_version_list = map(only_int, current_version.split('.'))
+    for min_ver in map(int, min_version.split('.')):
+      ver = current_version_list.pop(0)
+      if ver < min_ver:
+        return (False, current_version)
+      elif ver > min_ver:
+        return (True, current_version)
+    return (True, current_version)
+
 
 class SVN(object):
   COMMAND = "svn"
 
   @staticmethod
   def Run(args, in_directory):
     """Runs svn, sending output to stdout.
 
     Args:
       args: A sequence of command line parameters to be passed to svn.
@@ skipping 444 matching lines @@
     if not cur_dir_repo_root:
       return None
 
     while True:
       parent = os.path.dirname(directory)
       if (SVN.CaptureInfo(parent, print_error=False).get(
               "Repository Root") != cur_dir_repo_root):
         break
       directory = parent
     return GetCasedPath(directory)