Revert r104938 "Make svn update not prompt during a sync."

I'm not sure if it's causing the tree blow up but I'm not taking any chance.

TBR=dpranke@chromium.org
BUG=
TEST=

Review URL: http://codereview.chromium.org/8228017

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@104956 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/scm.py b/scm.py
index 875541f..fa73813 100644
--- a/scm.py
+++ b/scm.py
@@ -86,16 +86,7 @@
       return None
 
 
-def only_int(val):
-  if val.isdigit():
-    return int(val)
-  else:
-    return 0
-
-
 class GIT(object):
-  current_version = None
-
   @staticmethod
   def Capture(args, **kwargs):
     return subprocess2.check_output(
@@ -379,19 +370,23 @@
     root = GIT.Capture(['rev-parse', '--show-cdup'], cwd=cwd).strip()
     return os.path.abspath(os.path.join(cwd, root))
 
-  @classmethod
-  def AssertVersion(cls, min_version):
+  @staticmethod
+  def AssertVersion(min_version):
     """Asserts git's version is at least min_version."""
-    if cls.current_version is None:
-      cls.current_version = cls.Capture(['--version']).split()[-1]
-    current_version_list = map(only_int, cls.current_version.split('.'))
+    def only_int(val):
+      if val.isdigit():
+        return int(val)
+      else:
+        return 0
+    current_version =  GIT.Capture(['--version']).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, cls.current_version)
+        return (False, current_version)
       elif ver > min_ver:
-        return (True, cls.current_version)
-    return (True, cls.current_version)
+        return (True, current_version)
+    return (True, current_version)
 
 
 class SVN(object):
@@ -928,19 +923,24 @@
       directory = parent
     return GetCasedPath(directory)
 
-  @classmethod
-  def AssertVersion(cls, min_version):
+  @staticmethod
+  def AssertVersion(min_version):
     """Asserts svn's version is at least min_version."""
-    if cls.current_version is None:
-      cls.current_version = cls.Capture(['--version']).split()[2]
-    current_version_list = map(only_int, cls.current_version.split('.'))
+    def only_int(val):
+      if val.isdigit():
+        return int(val)
+      else:
+        return 0
+    if not SVN.current_version:
+      SVN.current_version = SVN.Capture(['--version']).split()[2]
+    current_version_list = map(only_int, SVN.current_version.split('.'))
     for min_ver in map(int, min_version.split('.')):
       ver = current_version_list.pop(0)
       if ver < min_ver:
-        return (False, cls.current_version)
+        return (False, SVN.current_version)
       elif ver > min_ver:
-        return (True, cls.current_version)
-    return (True, cls.current_version)
+        return (True, SVN.current_version)
+    return (True, SVN.current_version)
 
   @staticmethod
   def Revert(repo_root, callback=None, ignore_externals=False):